Positive type resist composition for use in liquid immersion exposure and a method of forming the pattern using the same

ABSTRACT

A positive type resist composition for use in liquid immersion exposure comprises: (A) a resin having a monocyclic or polycyclic cycloaliphatic hydrocarbon structure, the resin increasing its solubility in an alkali developer by an action of acid; (B) a compound generating acid upon irradiation with one of an actinic ray and a radiation; (C) an alkali soluble compound having an alkyl group of 5 or more carbon atoms; and (D) a solvent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation application of U.S. application Ser. No.13/782,148 filed Mar. 1, 2013, which is a Continuation of U.S.application Ser. No. 13/228,135 filed Sep. 8, 2011, now U.S. Pat. No.8,426,109, which is a Continuation of U.S. application Ser. No.12/325,472 filed Dec. 1, 2008, now U.S. Pat. No. 8,039,197, which is aContinuation of application Ser. No. 11/175,366 filed Jul. 7, 2005, nowU.S. Pat. No. 7,531,287, which claims priority under 35 U.S.C. §119 fromJP 2004-200679, filed Jul. 7, 2004, the disclosures of all of the aboveapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a positive type resist composition foruse in the step of manufacturing a semiconductors such as IC, andlithographic steps for the manufacture of circuit substrates, forexample, in liquid crystals and thermal heads and other photoapplications, as well as a method of forming a pattern using the same.Particularly, it relates to a positive type resist composition suitableto exposure by a liquid immersion type projection exposure systems usingfar UV-light at a wavelength of 300 nm or less as a light source, aswell as a method of forming the pattern using the same.

2. Description of the Related Art

Along with refinement of semiconductor devices, development has beenconducted for making the wavelength of a exposure light source shorterand making the numerical aperture of a projection lens higher (high NA),and a developing apparatus having NA of 0.84 using, as a light source,an ArF excimer laser having a wavelength at 193 nm has been developed atpresent. The resolution and the focal depth can be represented by thefollowing equations.

(Resolution)=k _(i)·(λ/NA)

(Focal depth)=±k ₂ ·λ/NA ²,

where λ is wavelength of an exposure light source, NA is a numeralaperture of a projection lens, and k₁ and k₂ are coefficients related toa process.

An exposure apparatus using an F₂ excimer laser having a wavelength at157 nm as a light source has now under investigation for attaininghigher resolution by making the wavelength further shorter but since thelens material used for the exposure apparatus and the material used forthe resist are extremely restricted for shorting the wavelength,reduction of the manufacturing cost for the apparatus and the materialand for stabilization of quality are extremely difficult, which haveresulted in the possibility that exposure apparatus and resist havingsufficient performance and stability can not be in time for therequested term.

As a technique for improving the resolution of an optical microscope, aso-called liquid immersion method has been known so far of filling aliquid of high refractive index (hereinafter also referred to as “liquidimmersion solution”) between a projection lens and a specimen.

For the “effect of liquid immersion”, the resolution and the focal depthdescribed above can be represented by the following equations in a caseof liquid immersion assuming the wavelength of exposure light in air asλ₀, the reflective index of the liquid immersion solution to air as n, aconversing semi-angle of a light as θ, and NA₀=sin θ:

(Resolution)=k ₁·(λ₀ /n)/NA ₀

(Focal depth)=±k ₂·(λ₀ /n)/NA ₀ ²

That is, the effect of the liquid immersion is equivalent with that inthe case of using 1/n exposure wavelength. In other words, the focaldepth can be increased to n times by liquid immersion in a case of aprojection optical system of identical NA.

This is effective to all sorts of pattern shapes and, further, can becombined with super resolution technique such as a phase shift method, amodified illumination method, etc. which have been under investigationat present.

Examples of apparatus applying the effects described above to thetransfer of fine patterns of semiconductor devices are described in JP-ANo. 57-153433, JP-A No. 7-220990, etc., but they do not describedresists suitable to the liquid immersion technique.

JP-A No. 10-303114 points out that control for the refractive index ofthe liquid immersion solution is important since the change of therefractive index of the liquid immersion solution causes degradation ofprojected images due to spherical aberration of exposure apparatus anddiscloses control of the temperature coefficient of the refractive indexof the liquid immersion solution to a certain range, and water withaddition of additives for lowering the surface tension or increasing thesurface activity as a suitable liquid immersion solution. However,disclosure of the additives or the resist suitable to the liquidimmersion exposure technique is not discussed.

Development of the recent liquid immersion exposure technique isreported, for example, in Bulletin of the International Society forOptical Engineering (Proc. SPIE), 2002, Vol. 4688, p 11, and J. Vac.Sci. Tecnol. B, 17 (1999), etc. In a case of using an ArF excimer laseras a light source, it is considered that pure water (refractive index at193 nm of 1.44) is considered most prospective as a liquid immersionsolution with a view point of handling safety, and transmittance andrefractive index at 193 nm.

In a case of using an F₂ excimer laser as a light source, while asolution containing fluorine has been considered in view of the balancebetween the transmittance and the refractive index at 157 nm, nosatisfactory solution in view of the circumstantial safety and therefractive index has yet been found. In view of the degree of the effectof liquid immersion and the degree of completion of the resist, it isconsidered that the liquid immersion exposure technique will be adoptedat first to the ArF exposure apparatus.

Since the resist for use in a KrF excimer laser (248 nm), an imageforming method of chemical amplification is used as a method of formingresist images in order to compensate the lowering of sensitivity causedby light absorption. Referring to the example of the image formingmethod of the positive type chemical amplification, this is an imageforming method of decomposing an acid generator in an exposed area byexposure to generate an acid, converting the alkali insoluble group intoan alkali soluble group by Post Exposure Bake (PEB) using the generatedacid as a reaction catalyst and removing the exposed area by alkalidevelopment.

In the liquid immersion exposure, a resist film is exposed through aphotomask in a state where a space between the resist film and theoptical lens is filled with the dipping solution (also referred to as aliquid immersion solution) to transfer the pattern of the photomask tothe resist film. However, it is anticipated that the dipping solutionpermeates inside the resist film thereby giving undesired effect on theperformance of the resist.

When a chemical amplification resist is applied to the liquid immersionexposure technique, the acid on the resist surface generated duringexposure is transferred to the liquid immersion solution to change theconcentration of the acid at the surface of the exposed area. It isconsidered that this is extremely similar with acid deactivation on thesurface of the exposure area caused by basic contamination of anextremely small amount at several ppb level from the circumstance duringPost Exposure time Delay (PED) which caused a significant problem in theinitial stage of the development of the chemical amplification typepositive resist but the effect and the mechanism given by the liquidimmersion exposure on the resistor have not yet been apparent.

On the other hand, in a case of applying chemical amplification typeresist having no problem in the lithography by usual exposure to thepattern formation by the liquid immersion exposure, it has been foundproblems that development defects and development residues (scums) areformed, or leaching of the resist to the liquid immersion solutionoccurs.

SUMMARY OF THE INVENTION

In view of the foregoing problems in the prior art, the presentinvention intends to provide a positive type resist composition suitableto liquid immersion exposure capable of suppressing the formation ofdevelopment defects and scums, with preferably less leaching of resistingredients to the liquid immersion solution upon pattern formation byliquid immersion exposure, as well as a method of forming a patternusing the same.

The present invention provides a positive type resist composition foruse in liquid immersion exposure of the following constitution, as wellas a method of forming the pattern using the same, by which theforegoing object of the invention can be attained.

(1) A positive type resist composition for use in liquid immersionexposure comprising:(A) a resin having a monocyclic or polycyclic cycloaliphatic hydrocarbonstructure, the resin increasing its solubility in an alkali developer byan action of acid;(B) a compound generating an acid upon irradiation with one of anactinic ray and a radiation;(C) an alkali soluble compound having an alkyl group of 5 or more carbonatoms; and(D) a solvent.(2) A positive type resist composition for use in liquid immersionexposure as described in (1) above, wherein the alkali soluble compound(C) has at least one or more of fluorine atom.(3) A positive type resist composition for use in liquid immersionexposure as described in (2) above, wherein the alkyl group of thealkali soluble compound (C) has at least one or more of fluorine atom.(4) A positive type resist composition for use in liquid immersionexposure as described in any one of (1) to (3) above, wherein the alkalisoluble compound (C) has an alcoholic hydroxyl group in which thealcohol moiety is a fluorinated alcohol.(5) A positive type resist composition for use in liquid immersionexposure as described in any one of (1) to (4) above, wherein the alkalisoluble compound (C) has a carboxylic group.(6) A method of forming a pattern comprising: forming a resist film by aresist composition as described in any one of (1) to (5) above;subjecting the resist film to liquid immersion exposure, so as to form aexposed resist film; and developing the exposed resist film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an experimental apparatus for two-beaminterference exposure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is to be described specifically below.

In the description for a group (atomic group) in the presentspecification, description with no indication of “substituted ornot-substituted” includes those not having substituent and those havingsubstituent. For example, “alkyl group” includes not only an alkyl groupnot having a substituent (not-substituted alkyl group) but also an alkylgroup having a substituent (substituted alkyl group).

(A) Resin which is Decomposed by the Effect of an Acid and Increases theSolubility in an Alkali Developer (Also Referred to as an AcidDecomposable Resin(A))

A resin for use in a chemical amplification type resist membrane forliquid immersion exposure according to the invention is a resin having amonocyclic or polycyclic cycloaliphatic hydrocarbon structure which isdecomposed by the effect of an acid and increases the solubility in analkali developer (acid decomposable resin), and having a group which isdecomposed by the effect of an acid to generate an alkali soluble group(hereinafter also referred to as “an acid decomposable group” on themain chain or the side chain of the resin or on both of the main chainand the side chain. The resin of the invention can be preferably used,in particular, for an ArF liquid immersion exposure.

The alkali soluble group includes, for example, a carboxyl group, ahydroxyl group, and a sulfonic group.

a preferred group decomposable with an acid includes, for example, agroup in which a hydrogen atom of a —COOH group is substituted with agroup which is split with the acid.

The acid decomposable group preferably includes, for example, a cumylester group, an enol ester group, an acetal ester group and a tertiaryalkyl ester group, with the tertiary alkyl ester group being furtherpreferred.

The resin contained in the positive type resist composition for use inliquid immersion exposure of the invention is preferably a resin havinga group represented by the following general formula (I) as the groupwhich is decomposed by the effect of an acid to generate an alkalisoluble group (acid decomposable group):

In the general formula (I),

R₁ to R₃ each independently represents an alkyl group, a cycloalkylgroup, or an alkenyl group. At least two of R₁ to R₃ may bond with eachother to form a ring.

As the alkyl group of R₁ to R₃, an alkyl group of from 1 to 8 carbonatoms is preferred, and it includes, for example, a methyl group, ethylgroup, propyl group, n-butyl group, sec-butyl group, 2-hexyl group, andoctyl group.

The cycloalkyl group of R₁ to R₃ may be a monocyclic or polycyclic, andspecifically, it includes, groups having a monocyclo, bicyclo, tricycloor tetracyclo structure having 5 or more carbon atoms. The number ofcarbon atoms is preferably from 6 to 30 and particularly preferably,from 7 to 25 carbon atoms.

Preferred cycloalkyl groups of R₁ to R₃ are, for example, an adamantlygroup, noradamantyl group, decalin residue, tricyclodecanyl group,tetracyclododecanyl group, norbornyl group, cedrol group, cyclohexylgroup, cycloheptyl group, cyclooctyl group, cyclodecanyl group, andcyclododecanyl group. More preferred are an adamantyl group,noradamantyl group, decalin residue, tricyclodecanyl group,tetracyclodecanyl group, norbornyl group, cedrol group, cyclohexylgroup, cycloheptyl group, cyclooctyl group, cyclodecanyl group andcyclododecanyl group. A portion of a hydrocarbon in the cycloalkyl groupmay be substituted with a hetero atom such as an oxygen atom.

Preferred alkenyl group of R₁ to R₃, an alkenyl group of from 2 to 8carbon atoms and includes, for example, a vinyl group, allyl group,butenyl group, and cyclohexenyl group.

The alkyl group, cycloalkyl group and alkenyl group of R₁ to R₃ may havea substituent. The substituent includes, for example, an alkyl group,halogen atom, hydroxyl group, alkoxy group, carboxyl group,alkoxycarbonyl group, cyano group, and ester group. As the alkyl group,a lower alkyl group such as a methyl group, ethyl group, propyl group,isopropyl group and butyl group are preferred, and more preferably amethyl group, ethyl group, propyl group and isopropyl group. The alkoxylgroup includes, for example, those having from 1 to 4 carbon atoms suchas a methoxy group, ethoxy group, propoxy group, and butoxy group. Thealkyl group and the alkoxy group may further have a substituent. Thesubstituent which may be present in the alkyl group and the alkoxylgroup includes, for example, a hydroxyl group, halogen atom, and alkoxygroup.

At least two of R₁ to R₃ may be bonded with each other to form a ring,in which they may be bonded by way of a hetero atom such as an oxygenatom.

The repetitive unit having the group represented by the general formula(I) may be any repetitive unit, and a repetitive unit represented by thefollowing general formula (pA) is preferred.

In the general formula (pA), R represents a hydrogen atom, a halogenatom or an alkyl group having from 1 to 4 carbon atoms. Plural R may beidentical with or different from each other.

A represents a group selected from a single bond, alkylene group, ethergroup, thioether group, carbonyl group, ester group, amide group,sulfoneamide group, urethane group and urea group, alone or incombination of two or more of them. The alkylene group may have asubstituent.

R₁ to R₃ have the same meanings as those for R₁ to R₃ defined in thegeneral formula (I).

The repetitive unit represented by the general formula (pA) is, mostpreferably, a repetitive unit derived from2-alkyl-2-adamantyl(meth)acrylate ordialkyl(1-adamantyl)methyl(meth)acrylate.

Specific examples of the repetitive unit represented by the generalformula (pA) is shown below.

(where Rx represents H, CH₃ or CF₃.)

In the acid decomposable resin (A), the content of the repetitive grouphaving the group represented by the general formula (I) is preferably,from 10 to 60 mol %, more preferably, from 1 to 50 mol % in the totalrepetitive units.

The acid decomposable resin (A) may have only the group represented bythe general formula (I) as the acid decomposable group, or may have anyother acid decomposable group in combination.

The other acid decomposable group which may be present in thedecomposable resin (A) includes, for example, —O—C(R₃₆)(R₃₇)(R₃₈),—O—C(R₃₆)(R₃₇)(OR₃₉), —O—C(═O)—O—C(R₃₆)(R₃₇)(R₃₈), —O—C(R₀₁)(R₀₂)(OR₃₉),—O—C(R₀₁)(R₀₂)—C(═O)—O—C(R₃₆)(R₃₇)(R₃₈).

In the formula, R₃₆ to R₃₉ each independently represents an alkyl group,a cycloalkyl group, aryl group, aralkyl group or alkenyl group. R₃₆ andR₃₇, and R₃₈ and R₃₉ may be bonded with each other to form a ring.

R₀₁ and R₀₂ each independently represents a hydrogen atom, an alkylgroup, cycloalkyl group, aryl group, aralkyl group or alkenyl group.

—C(R₃₆)(R₃₇)(R₃₈) represents a group in which each group represented byR₃₆ to R₃₈ is bonded to a carbon atom by way of a single bond, here andhereinafter.

For the acid decomposable resin (A), the total amount of the repetitiveunits having an acid decomposable group including a repetitive unithaving an acid decomposable group represented by the general formula(I), as well as a repetitive unit having any other acid decomposablegroup is preferably from 10 to 70 mol %, more preferably, from 20 to 65mol %, further more preferably from 25 to 50 mol % based on the totalrepetitive units.

The monocyclic or polycyclic cycloaliphatic hydrocarbon structurecontained in the acid decomposable resin (A) includes, although notparticularly restricted, a cycloalkyl group as R₁ to R₃ in the formula(I) described above and a cycloaliphatic hydrocarbon structure presentin the repetitive unit to be described below.

The acid decomposable resin (A) preferably has at least one unit, as therepetitive unit having a monocyclic or polycyclic cycloaliphatichydrocarbon structure, selected from the group consisting of repetitiveunits having a partial structure containing a cycloaliphatic hydrocarbonrepresented by the following general formula (pI) to the general formula(pVI) and repetitive units represented by the following general formula(II-AB).

At first, the partial structure containing a cycloaliphatic hydrocarbonrepresented by the general formula (pI) to the general formula (pVI) isto be described.

In the formula, R₁₁ represents a methyl group, ethyl group, n-propylgroup, isopropyl group, n-butyl group, isobutyl group or sec-butylgroup, and Z represents an atomic group necessary for forming acycloaliphatic hydrocarbon group together with a carbon atom.

R₁₂ to R₁₆ each independently represents a linear or branched alkylgroup of 1 to 4 carbon atoms or a cycloaliphatic hydrocarbon group,providing that at least one of R₁₂ to R₁₄, or either R₁₅ or R₁₆represents a cycloaliphatic group.

R₁₇ to R₂₁ each independently represents a hydrogen atom, a linear orbranched alkyl group of 1 to 4 carbon atoms or a cycloaliphatichydrocarbon group, providing that at least one of R₁₇ to R₂₁ representsa cycloaliphatic hydrocarbon group. Further, either R₁₉ or R₂₁represents a linear or branched alkyl group of 1 to 4 carbon atoms.

R₂₂ to R₂₅ each independently represents a hydrogen atom or a linear orbranched alkyl group of 1 to 4 carbon atoms or a cycloaliphatichydrocarbon group, providing that at least one of R₂₂ to R₂₅ representsa cycloaliphatic group. R₂₂ and R₂₄ may join with each other to form aring.

The cycloaliphatic hydrocarbon group for R₁₁ to R₂₅ or thecycloaliphatic hydrocarbon group which is formed by Z and carbon atomsmay be monocyclic or polycyclic. Specifically, it includes groups havinga monocyclo, bicyclo, tricyclo, or tetracyclo structure of 5 or morecarbon atoms. The number of carbon atoms thereof is preferably from 6 to30 and, particularly preferably, 7 to 25. The cycloaliphatic hydrocarbongroups may have a substituent.

Preferred cycloaliphatic hydrocarbon group are an adamantly group,noradamantyl group, decalin residue, tricyclodecanyl group,tetracyclododecanyl group, norbornyl group, cedrol group, cyclohexylgroup, cycloheptyl group, cyclooctyl group, cyclodecanyl group, andcyclododecanyl group. More preferred are the adamantly group, decalinresidue, norbornyl group, cedrol group, cyclohexyl group, cycloheptylgroup, cyclooctyl group, cylodecanyl group, and cyclododecanyl group.

The substituent which may be present in the cycloaliphatic hydrocarbongroups described above includes, for example, an alkyl group, halogenatom, hydroxyl group, alkoxy group, carboxyl group, and alkoxycarbonylgroup. The alkyl group is preferably, lower alkyl groups such as methylgroup, ethyl group, propyl group, isopropyl group, and butyl group and,more preferably, selected from the group consisting of a methyl group,ethyl group, propyl group and isopropyl group. The alkoxyl groupincludes, for example, those having 1 to 4 carbon atoms such as amethoxy group, ethoxy group, propoxy group, and butoxy group. Thesubstituent which may further be present in the alkyl group, alkoxygroup and alkoxycarbonyl group, includes, for example, a hydroxyl group,halogen atom and alkoxy group.

The structure represented by the general formulae (pI) to (pVI) in theresin can be used for the protection of the alkali soluble group. Thealkali soluble group include various groups known in the relevanttechnical field.

Specifically, the alkali soluble group includes, for example, acarboxylic acid group, sulfonic acid group, phenol group and thiolgroup, and the carboxylic acid group and the sulfonic acid group arepreferred.

The alkali soluble group protected by the structure represented by thegeneral formulae (pI) to (pVI) in the resin includes, preferably, astructure in which the hydrogen atom of the carboxyl group issubstituted with the structure represented by the general formulae (pI)to (pVI).

Specific examples of the repetitive units having the structure in whichthe hydrogen atom of the carboxyl group is substituted with thestructure represented by the general formulae (pI) to (pVI) include, forexample, those identical with the specific examples of the repetitiveunits represented by the general formula (pA).

It is more preferred that the resin of the ingredient (A) contains therepetitive units having a group represented by the general formula (1A).

In the formula (IA),

R_(x) represents a hydrogen atom or a methyl group.

R_(y) represents an alkyl group of 1 to 6 carbon atoms. The alkyl groupof 1 to 6 carbon atoms in R_(y) may be linear or branched, and may benot substituted, or may have a further substituent. The substituentwhich may be present in the alkyl group is, for example, an alkoxy groupof 1 to 4 carbon atoms, halogen atom (fluorine atom, chlorine atom,bromine atom, or iodine atom), acyl group, acyloxy group, cyano group,hydroxyl group, carboxyl group, alkoxycarbonyl group, or nitro group.

The repetitive unit represented by the formula (IA) includes repetitiveunits derived from 2-methyl-2-adamantyl(meth)acrylate,2-ethyl-2-adamantyl(meth)acrylate, 2-propyl-2-adamantyl(meth)acrylate,2-isopropyl-2-adamantyl(meth)acrylate,2-butyl-2-adamantyl(meth)acrylate, and2-(3-methoxypropyl)-2-adamantyl(meth)acrylate. Preferred are repetitiveunits derived from 2-methyl-2-adamantyl(meth)acrylate or2-ethyl-2-adamantyl(meth)acrylate.

Next, the repetitive units having a cycloaliphatic structure representedby the general formula (II-AB) are to be described.

In the formula (II-AB):

R₁₁′ and R₁₂′ each independently represents a hydrogen atom, cyanogroup, halogen atom, or alkyl group.

Z′ represents an atomic group containing two bonded carbon atoms (C—C),and for forming a cycloaliphatic structure.

Furthermore, the repetitive unit represented by the general formula(II-AB) is preferably repetitive units represented by the followinggeneral formula (II-A) or the general formula (II-B).

In the formulae (II-A) and (II-B):

R₁₃′ to R₁₆′ each independently represents a hydrogen atom, halogenatom, hydroxyl group, cyano group, —COOH, —COOR₅, a group which isdecomposed by the action of an acid, —C(═O)—X-A′-R₁₇′, alkyl group orcyclic hydrocarbon group, in which

R₅ represents an alkyl group, a cyclic hydrocarbon group or thefollowing —Y group.

X represents an oxygen atom, sulfur atom, —NH—, or —NHSO₂— or —NHSO₂NH—.

A′ represents a single bond or a bivalent bonding group.

Further, at least two members of R₁₃′ to R₁₆′ may join to form a ring. nis 0 or 1.

R₁₇′ represents —COOH, —COOR₅, —CN, hydroxyl group, alkoxy group,—CO—NH—R₆, —CO—NH—SO₂—R₆ or the following —Y group.

R₆ represents an alkyl group or a cyclic hydrocarbon group.

—Y group;

in the —Y group, R₂₁′ to R₃₀′ each independently represents a hydrogenatom or alkyl group. a and b each presents 1 or 2.

In the general formulae (pI) to (pVI), the alkyl group for R₁₂ to R₂₅ isa linear or branched alkyl group having 1 to 4 carbon atoms. The alkylgroup includes, for example, a methyl group, ethyl group, n-propylgroup, isopropyl group, n-butyl group, isobutyl group, sec-butyl group,and t-butyl group.

Furthermore, the substituent which may be present in each of the alkylgroups includes, for example, an alkoxy group of 1 to 4 carbon atoms,halogen atom (fluorine atom, chlorine atom, bromine atom or iodineatom), acyl group, acyloxy group, cyano group, hydroxyl group, carboxygroup, alkoxycarbonyl, group and nitro group.

In the general formula (II-AB), R₁₁′ and R₁₂′ each independentlyrepresents a hydrogen atom, cyano group, halogen atom or alkyl group.

Z′ represents an atomic group containing two bonded carbon atoms (C—C),and for forming a cycloaliphatic structure.

The halogen atom in the R₁₁′ and R₁₂′ includes, for example, a chlorineatom, bromine atom, fluorine atom, and iodine atom.

The alkyl group for the R₁₁′, R₁₂′, and R₂₁′ to R₃₀′ is preferably alinear or branched alkyl group of 1 to 10 carbon atoms, more preferably,linear or branched alkyl group of 1 to 6 carbon atoms, and furtherpreferably, a methyl group, ethyl group, propyl group, isopropyl group,n-butyl group, isobutyl group, sec-butyl group, and t-butyl group.

A further substituent in the alkyl group includes, for example, ahydroxyl group, halogen atom, carboxyl group, alkoxy group, acyl group,cyano group, and acyloxy group. The halogen atom includes, for example,a chlorine atom, bromine atom, fluorine atom, and iodine atom, thealkoxy group includes those having 1 to 4 carbon atoms, for example, amethoxy group, ethoxy group, propoxy group and butoxy group, the acylgroup includes, for example, a formyl group and acetyl group, and theacyloxy group includes, for example, an acetoxy group.

The atomic group for forming the cycloaliphatic structure of Z′ is anatomic group forming repetitive units of a cycloaliphatic hydrocarbonwhich may also have a substituent and, among them, an atomic group forforming a bridged cycloaliphatic structure forming repetitive units ofthe bridged cycloaliphatic is preferred.

Skeletons of the cycloaliphatic hydrocarbon to be formed can includethose identical with the cycloaliphatic hydrocarbon group for R₁₁ to R₂₅in the general formulae (pI) to (pVI).

The skeleton of the cycloaliphatic hydrocarbon may have a substituent.Such substituent includes R₁₃′ to R₁₆′ in the general formula (II-A) or(II-B).

Among the repetitive units having the bridged cycloaliphatichydrocarbon, repetitive units represented by the general formula (II-A)or (II-B) described above are more preferred.

In the repetitive units represented by the general formula (II-AB), theacid decomposable group may be contained in the —C(═O)—X-A′-R₁₇′, or maybe contained as a substituent present in the cycloaliphatic structureformed by Z′.

The structure of the acid decomposable group is represented by—C(═O)—X₁—R₀.

In the formula, R₀ represents a tertiary alkyl group such as t-butylgroup, or t-amyl group, 1-alkoxyethyl group such as isobornyl group,1-ethoxyethyl group, 1-butoxyethyl group, 1-isobutoxyethyl group, or1-cyclohexyloxyethyl group, an alkoxymethyl group such as1-methoxymethyl group or 1-ethoxymethyl group, 3-oxoalkyl group,tetrahydropyranyl group, tetrahydrofuranyl group, trialkyl silyl estergroup, 3-oxo cyclohexyl ester group, 2-methyl-2-adamantyl group, ormevalonic lactone residue. X₁ is as defined for the X.

The halogen atom for the R₁₃′ to R₁₆′ is a chlorine atom, bromine atom,fluorine atom or iodine atom.

The alkyl group for the R₅, R₆ and R₁₃′ to R₁₆′ is preferably a linearor branched alkyl group of 1 to 10 carbon atoms, more preferably, linearor branched alkyl groups of 1 to 6 carbon atoms, and further preferably,methyl group, ethyl group, propyl group, isopropyl group, n-butyl group,isobutyl group, sec-butyl group, and t-butyl group.

The cyclic hydrocarbon group for R₅, R₆ and R₁₃ to R₁₆′ includes, forexample, an alkyl group and bridged hydrocarbon, and includes, forexample, cyclopropyl group, cyclopentyl group, cyclohexyl group,adamantly group, 2-methyl-2-adamantyl group, norbornyl group, bornylgroup, isobornyl group, tricyclodecanyl group, dicyclopentenyl group,norbornane epoxy group, menthyl group, isomentyl group, neomentyl groupand tetracyclododecanyl group.

Among R₁₃′ to R₁₆′, a ring formed by bonding at least two of themincludes, for example, rings of 5 to 12 carbon atoms such ascyclopentene, cyclohexene, cycloheptane and cyclooctane.

The alkoxy group for R₁₇′ includes, for example, those of 1 to 4 carbonatoms such as methoxy group, ethoxy group, propoxy group and butoxygroup.

An additional substituent for the alkyl group, cyclic hydrocarbon groupor alkoxy group includes, for example, hydroxyl group, halogen atom,carboxyl group, alkoxy group, acyl group, cyano group, acyloxy group,alkyl group or cyclic hydrocarbon group. The halogen atom includes ischlorine atom, bromine atom, fluorine atom, or iodine atom. The alkoxygroup includes those of 1 to 4 carbon atoms such as methoxy group,ethoxy group, propoxy group and butoxy group, and the acyl groupincludes, for example, formyl group and acetyl group, and the acyloxygroup includes, for example, acetoxy group.

The alkyl group and cyclic hydrocarbon group includes those describedabove.

The bivalent connection group for A′ includes, for example, a groupselected from the group consisting of alkylene group, ether group,thioether group, carbonyl group, ester group, amide group, sulfoneamidegroup, urethane group and urea group, or a combination of two or more ofthem.

Various kinds of substituents for R₁₃′ to R₁₆′ in the general formula(II-A) or (II-B) may also be a substituent for the atomic group forforming the cycloaliphatic structure or an atomic group Z for forming abridged cycloaliphatic structure.

Specific examples of the repetitive units represented by the generalformula (II-A) or (II-B) include the following units, but the inventionis not restricted to those specific examples.

Among the acid decomposable resins (A), the content of repetitive unitshaving a partial structure including the cycloaliphatic hydrocarbonsrepresented by the general formulae (pI) to (pVI) is preferably from 20to 70 mol %, more preferably, 24 to 65 mol %, and, further, preferably28 to 60 mol % in the entire repetitive structural units.

In the acid decomposable resin (A), the content of the repetitive unitsrepresented by the general formula (II-AB) is preferably from 10 to 60mol %, more preferably, from 15 to 55 mol % and, further preferably,from 20 to 50 mol % in the entire repetitive structural units.

In the acid decomposable resin (A) having the monocyclic or polycycliccycloaliphatic hydrocarbon structure, the acid decomposable grouprepresented by the general formula (I) and other decomposing groups maybe present in any of the repetitive units having the partial structurecontaining the cycloaliphatic hydrocarbon represented by the generalformula (pI) to general formula (pVI), repetitive units represented bythe general formula (II-AB), and repetitive units of othercopolymerization ingredients to be described later.

Further, the acid decomposable resin (A) preferably has a lactone groupand, more preferably, has repetitive units having a group having alactone structure represented by the following general formula (Lc) orany one of the following general formulae (III-1) to (III-5), in whichthe group having the lactone structure may be bonded directly to themain chain.

In the general formula (Lc), Ra₁, Rb₁, Rc₁, Rd₁, and Re₁ each representshydrogen atom or alkyl group. m and n each independently represents aninteger of from 0 to 3, and m+n is 2 or more and 6 or less.

In the general formula (III-1) to (III-5), R_(1b) to R_(5b) eachindependently represents hydrogen atom, alkyl group, cycloalkyl group,alkoxy group, alkoxycarbonyl group, alkylsulfonylimino group or alkenylgroup. Two members of R_(1b) to R_(5b) may join to form a ring.

The alkyl group for Ra₁ to Re₁ in the general formula (Lc) and the alkylgroup for the alkyl group, alkoxy group, alkoxycarbonyl group oralkylsulfonylimino group for R_(1b) to R_(5b) include linear or branchedalkyl groups which may have a substituent.

A preferred substituent includes, for example, alkoxy group of 1 to 4carbon atom, halogen atom (fluorine atom, chlorine atom, bromine atom,or iodine atom), acyl group of 2 to 5 carbon atoms, acyloxy group of 2to 5 carbon atoms, cyano group, hydroxyl group, carbonyl group,alkoxycarbonyl group of 2 to 5 carbon atoms, and nitro group.

The repetitive unit containing a group having a lactone structurerepresented by the general formula (Lc) or any one of the generalformulae (III-1) to (III-5) includes, for example, those in which atleast one of R₁₃′ to R₁₆′ in the general formula (II-A) or the generalformula (II-B) has a group represented by the general formula (III-1) to(III-5) (for example, a group in which R₅ in —COOR₅ is a grouprepresented by the general formula (Lc) or the general formulae (III-1)to (III-5)), or a repetitive unit represented by the following generalformula (AI).

In the general formula (AI), R_(b0) represents hydrogen atom, halogenatom or alkyl group of 1 to 4 carbon atoms. A preferred substituentwhich may be present in the alkyl group for R_(b0) includes thosepreviously exemplified as preferred substituents which may be present inthe alkyl group for R_(1b) in the general formulae (III-1) to (III-5).

The halogen atom for R_(b0) is fluorine atom, chlorine atom, bromineatom, or bromine atom. R_(b0) is, preferably, hydrogen atom.

A′ represents single bond, ether bond, ester bond, carbonyl group,alkylene group or bivalent group of the combination of them.

B₂ represents a group represented by the general formula (Lc) or any oneof the general formulae (III-1) to (III-5).

Specific examples of the repetitive unit containing the group having alactone structure are to be described below, but the invention is notrestricted to them.

The acid decomposable resin (A) may contain a repetitive unit having agroup represented by the following general formula (IV).

In the general formula (IV), R_(2c) to R_(4c) each independentlyrepresents hydrogen atom or hydroxyl group, providing that at least oneof R_(2c) to R_(4c) represents hydroxyl group.

The group represented by the general formula (IV) is preferably, of adihydroxy form or monohydroxy form, more preferably, of a dihydroxyform.

The repetitive unit having a group represented by the general formula(IV) includes, for example, those having a group in which at least oneof R₁₃′ to R₁₆′ in the general formula (II-A) or (II-B) has a grouprepresented by the general formula (IV) (for example, R₅ in —COOR₅ is agroup represented by the general formula (IV)), or repetitive unitsrepresented by the following general formula (AII).

In the general formula (AII), R_(1c) represents hydrogen atom or methylgroup.

R_(2c) to R_(4c) each independently represents hydrogen atom or hydroxylgroup, providing that at least one of R_(2c) to R_(4c) representshydroxyl group and preferably, two members of R_(2c) to R_(4c) eachrepresents hydroxyl group.

Specific examples of the repetitive unit having the structurerepresented by the general formula (AII) are shown below, but they arenot limited to them.

The acid decomposable resin (A) may have a repetitive unit representedby the following general formula (V).

In the general formula (V), Z₂ represents —O— or —N(R₄₁)—. R₄₁represents hydrogen atom, hydroxyl group, alkyl group or —OSO₂—R₄₂. R₄₂represents alkyl group, cycloalkyl group or camphor residue. The alkylgroup, cycloalkyl group, or camphor residue for R₄₁ or R₄₂ may besubstituted with halogen atom (preferably, fluorine atom).

The repetitive unit represented by the general formula (V) includesthose specific examples below, but they are not restricted to them.

The acid decomposable resin (A) can contain, in addition to therepetitive structural units described above, various repetitivestructural units with an aim of controlling the dry etching resistance,standard liquid developer adaptability, substrate adhesion property,resist profile and, further, resolution, heat resistance, sensitivity,etc. which are generally necessary characteristics of the resist.

Such repetitive structural units include the repetitive structural unitcorresponding to the following monomers, but they are not restricted tothem.

This enables for fine control of the performance required for the resinof the ingredient (A), especially,

(1) solubility to a coating solvent,(2) film-forming property (glass transition point),(3) alkali developability,(4) film reduction (selection of hydrophilic/phobic property, alkalisolubility group selection),(5) adhesion to substrate at not exposed area,(6) dry etching resistance, etc.

Such monomers include compounds having one addition polymerizableunsaturated bond selected, for example, from acrylate esters,methacrylate esters, acrylamides, methacrylamides, allyl compounds,vinyl ethers, and vinyl esters.

In addition, any of addition polymerizable compounds that arecopolymerizable with the monomer corresponding to the various repetitivestructural units described above also may be copolymerized.

In the acid decomposable resin A, the molar ratio of each of therepetitive structural units contained is properly set so as to controlthe dry etching resistance or adaptability to standard liquid developer,a substrate adhesion, profile of the resist and, further, resolution,heat resistance, sensitivity, etc. which are general necessaryperformances of the resist.

While the content of the repetitive structural units based on themonomers of the further copolymerizable ingredients in the resin canalso be set appropriately depending on the desired performances of theresist, generally, it is preferably 99 mol % or less, more preferably,90 mol % or less, further preferably, 80 mol % or less based on thetotal mol number of the repetitive structural units having a partialstructure containing cycloaliphatic hydrocarbon represented by thegeneral formulae (pI) to (pVI) and the repetitive units represented bythe general formula (II-AB).

The content especially of the repetitive units containing a group havingthe lactone structure described above and the repetitive unitscontaining the group represented by the general formula (IV)(hydroxyadamantane structure) is as follows.

Based on the summed total mol number of the repetitive structural unitshaving a partial structure containing the cycloaliphatic hydrocarbonrepresented by the general formulae (pI) to (pVI) and the repetitiveunits represented by the general formula (II-AB),

the content of the repetitive units containing a group having thelactone structure is preferably from 1 to 70 mol %, more preferably,from 10 to 70 mol %, and

the content of the repetitive units containing the group represented bythe general formula (IV) is preferably, from 1 to 70 mol %, morepreferably, from 1 to 50 mol %.

In a case where the composition of the invention is for exposure to ArF,it is preferred that the resin has no aromatic group in view oftransparency to ArF light.

The acid decomposable resin (A) can be synthesized by ordinary method(for example, radical polymerization).

For example, the general synthesis method comprises charging monomerspecies into a reaction vessel collectively or in the course of thereaction, dissolving them, for example, in ethers such astetrahydrofuran, 1,4-dioxane, and diisopropyl ether, ketones such asmethyl ethyl ketone, and methyl isobutyl ketone, ester solvents such asethyl acetate and further, in a solvent that dissolves the compositionof the invention such as propylene glycol monomethyl ether acetate to bedescribed later, making them uniform, then optionally carrying outheating in an inert gas atmosphere such as of nitrogen or argon andstarting polymerization by using a commercially available radicalinitiator (such as azo type initiator, peroxides, etc.). If required, aninitiator is add or added divisionally and, after completing thereaction, the reaction product is charged into a solvent and the desiredpolymer is recovered by a method such as in the form of power or solid.The concentration in the reaction is usually 20 mass % or more,preferably, 30 mass % or more, further preferably, 40 mass % or more.The temperature for the reaction is usually from 10° C. to 150° C.,preferably, from 30° C. to 120° C., further preferably, from 50 to 100°C.

The repetitive structural units may be used each alone, or may be usedas a combination of a plurality of them. In addition, the resin may beused alone, or may be used as a combination of a plurality of them.

The weight average molecular weight of the acid decomposable resin (A),on the basis of polystyrene by a gas permeation chromatography (GPC)method, is preferably from 1,000 to 200,000, more preferably, from 3,000to 20,000. By determining the weight average molecular weight to 1,000or more, heat resistance and dry etching resistance can be improved, andby determining the weight average molecular weight to 200,000 or less,the developing property can be improved, and in addition, the viscosityis lowered to result in improvement of the film-forming property.

Referring to the molecular weight distribution (Mw/Mn, also referred toas dispersibility), those in a range usually, from 1 to 5, preferably,from 1 to 4, further preferably, from 1 to 3 are used. The molecularweight distribution is preferably 5 or less in view of the resolution,configuration of the resist, side wall of the resist pattern androughness.

The amount of residual monomers in the acid decomposable monomer (A) ispreferably, from 0 to 10 mass %, more preferably, from 0 to 5 mass %.

In the positive type resist composition of the invention, the blendingamount of the acid decomposable resin (A) is, preferably, from 40 to99.99 mass %, more preferably, from 50 to 99.97 mass % based on thetotal solid content of the resist.

(B) Compound Generating Acid Upon Irradiation with One of an Actinic Rayand a Radiation

The compound that generates acid upon irradiation with one of an actinicray and a radiation to be used for the positive type resist compositionfor use in immersion exposure according to the invention (hereinaftersometimes referred to as “acid generator”) is to be described below.

The acid generator used in the invention can be selected from thecompounds used generally as the acid generator.

That is, photoinitiator for photo-cationic polymerization,photoinitiator for photo-radical polymerization, light extinguishingagent for dyes, light discolorant, or known compounds that generate acidupon irradiation with one of an actinic ray and a radiation such as farUV-rays and X-rays used for microresist or the like, as well as mixturesthereof can be properly selected and used.

They include, for example, diazonium salt, phosphonium salt, sulfoniumsalt, iodonium salt, imidosulfonate, oximesulfonate, diazodisulfone,disulfone and o-nitrobenzylsulfonate.

For compounds in which the group or the compound generating an acid uponirradiation with one of an actinic ray and a radiation are introduced tothe main chain or the side chains of the polymer, for example, compoundsdescribed in U.S. Pat. No. 3,849,137, GP No. 3914407, JP-A Nos.63-26653, 55-164824, 62-69263, 63-146038, 63-163452, 62-153853, and63-146029 can be used.

In addition, compounds generating an acid by light described in U.S.Pat. No. 3,779,778 and EP No. 126,712 can also be used.

Preferred compounds, among the acid generating agents, include compoundsrepresented by the following general formulae (ZI), (ZII) and (ZIII).

In the general formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each independentlyrepresents an organic group.

X⁻ represents a non-nucleophilic anion.

The number of carbon atoms in the organic group as R₂₀₁, R₂₀₂ or R₂₀₃ isgenerally from 1 to 30, preferably, from 1 to 20.

Two members of R₂₀₁ to R₂₀₃ may join to form a ring structure, and thering may have an oxygen atom, sulfur atom, ester bond, amide bond, orcarbonyl group therein.

As the group formed by joining two members of R₂₀₁ to R₂₀₃ includes analkylene group (for example, butylene group or pentylene group).

Specific examples of the organic group as R₂₀₁, R₂₀₂, and R₂₀₃ include,for example, groups corresponding to those in the compounds (Z1-1),(Z1-2), and (Z1-3) to be described later.

Compounds having a plurality of structures represented by the generalformula (ZI) may also be adopted. For example, compounds having such astructure that at least one of R₂₀₁ to R₂₀₃ of the compounds representedby the general formula (ZI) joins with at least one of R₂₀₁ to R₂₀₃ ofother compounds represented by the general formula (ZI).

Further preferred (ZI) ingredients include compounds (Z1-1), (Z1-2), and(Z1-3) to be described below.

The compound (Z1-1) is an arylsulfonium compound in which at least oneof R₂₀₁ to R₂₀₃ of the general formula (ZI) is an aryl group, that is, acompound having arylsulfonium as a cation.

In the arylsulfonium compound, all of R₂₀₁ to R₂₀₃ may be an aryl group,and a portion of R₂₀₁ to R₂₀₃ may be an aryl group, and the residues maybe an aryl group and a cycloalkyl group.

The arylsuofonium compound includes, for example, triarylsulfoniumcompounds, diarylalkyl sulfonium compounds, aryldialkyl sulfoniumcompounds, diarylcycloalkyl sulfonium compounds, and aryldicycloalkylsulfonium compounds.

The aryl group of the arylsulfonium compound is, preferably, a phenylgroup and a naphthyl group and more preferably, a phenyl group. In acase where the arylsulfonium compound has two or more aryl groups, thetwo or more aryl groups may be identical with or different from eachother.

The alkyl group which is optionally present in the arylsulfoniumcompound is preferably a linear or branched alkyl group of from 1 to 15carbon atoms and includes, for example, a methyl group, ethyl group,propyl group, n-butyl group, sec-butyl group or t-butyl group.

The cycloalkyl group which is optionally present in the arylsulfoniumcompound is, preferably, a cycloalkyl group of from 3 to 15 carbon atomsand includes, for example, a cyclopropyl group, cyclobutyl group iscyclohexyl group.

The aryl group, alkyl group, or cycloalkyl group for R₂₀₁ to R₂₀₃ mayhave an alkyl group (for example, of 1 to 15 carbon atoms), cycloalkylgroup (for example, of 3 to 15 carbon atoms), aryl group (for example,of 6 to 14 carbon atoms), alkoxy group (for example, 1 to 15 carbonatoms), halogen atom, hydroxyl group or phenylthio group as asubstituent. The substituent includes, preferably, a linear or branchedalkyl group of 1 to 12 carbon atoms, cycloalkyl group of 3 to 12 carbonatoms, alkoxy group of 1 to 12 carbon atom, and, most preferably, analkyl group of 1 to 4 carbon atoms, and alkoxy group of 1 to 4 carbonatoms. The substituent may be substituted on any one of three members ofR₂₀₁ to R₂₀₃, and may be substituted on all of the three members. In acase where R₂₀₁ to R₂₀₃ each represents an aryl group, the substituentis preferably at the p-position of the aryl group.

The non-nucleophilic anion as X⁻ includes, for example, a sulfonic acidanion, carboxylic acid anion, sulfonylimide anion,bis(alkylsulfonyl)imide anion, and tris(alkylsulfonyl)methyl anion.

The non-nucleophilic anion means an anion with extremely low effect ofcausing nucleophilic reaction, which is an anion capable of suppressingaging decomposition by intra-molecular nucleophilic reaction.

The sulfonic acid anion includes, for example, an aliphatic sulfonicacid anion, aromatic sulfonic acid anion, or camphor sulfonic acidanion.

The carboxylic acid anion includes, for example, an aliphatic carboxylicacid anion, aromatic carboxylic acid anion, and aralkyl carboxylic acidanion.

The aliphatic group in the aliphatic sulfonic acid anion includes, forexample, an alkyl group of 1 to 3 carbon atoms, specifically, a methylgroup, ethyl group, propyl group, isopropyl group, n-butyl group,isobutyl group, sec-butyl group, pentyl group, neopentyl group, hexylgroup, heptyl group, octyl group, nonyl group, decyl group, undecylgroup, dodecyl group, tridecyl group, tetradecyl group, pentadecylgroup, hexadecyl group, heptadecyl group, octadecyl group, nonadecylgroup, eicosyl group and a cycloalkyl group of 3 from 30 carbon atoms,specifically, a cyclopropyl group, cyclopentyl group, cyclohexyl group,adamantyl group, norbornyl group, and boronyl group.

The aromatic group in the aromatic sulfonic acid anion include,preferably, aryl group of 6 to 14 carbon atoms, for example, a phenylgroup, tolyl group, and naphthyl group.

The alkyl group, cycloalkyl group and aryl group in the aliphaticsulfonic acid anion and aromatic sulfonic acid anion may have asubstituent.

Such substituent include, for example, a nitro group, halogen atom(fluorine atom, chlorine atom, bromine atom, or iodine atom), carboxylgroup, hydroxyl group, amino group, cyano group, alkoxy group(preferably of 1 to 5 carbon atoms), cycloalkyl group (preferably of 3to 15 carbon atoms), aryl group (preferably of 6 to 14 carbon atoms),alkoxycarbonyl group (preferably of 2 to 7 carbon atoms), acyl group(preferably of 2 to 12 carbon atoms), alkoxycarbonyl oxy group(preferably of 2 to 7 carbon atoms), and alkylthio group (preferably of1 to 15 carbon atoms). The aryl group and the ring structure which arepresent in each group may further include alkyl group preferably of 1 to15 carbon atoms as a substituent.

The aliphatic group in the aliphatic carboxylic acid anion includesthose identical with the aliphatic group in the aliphatic sulfonic acidanion.

The aromatic group in the aromatic carboxylic acid anion includes thoseidentical with the aromatic group in the aromatic sulfonic acid anion.

The aralkyl group in the aralkyl carboxylic acid anion includespreferably an aralkyl group of 6 to 12 carbon atoms, for example, benzylgroup, phenetyl group, naphthyl methyl group, naphthyl ethyl group, andnaphthyl methyl group.

The aliphatic group, aromatic group, and aralkyl group in the aliphaticcarboxylic acid anion, aromatic carboxylic acid anion, and aralkylcarboxylic acid anion may have a substituent, and the substituentincludes, for example, a halogen atom, alkyl group, cycloalkyl group,alkoxy group, and alkyl thio group, like those for the aliphaticsulfonic acid anion.

The sulfonylimide anion includes, for example, a saccharin anion.

The alkyl group in the bis(alkylsulfonyl)imide anion, andtris(alkylsulfonyl)methyl anion is preferably an alkyl group of 1 to 5carbon atoms and includes, for example, methyl group, ethyl group,propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butylgroup, pentyl group, and neopentyl group. Those alkyl groups may have asubstituent, and the substituent includes, a halogen atom, and alkylgroup, alkoxy group, and alkylthio group substituted with a halogenatom, and the alkyl group substituted with a fluorine atom is preferred.

Other non-nucleophilic anions include, for example, phosphorousfluoride, boron fluoride, and antimony fluoride.

The non-nucleophilic anion for X⁻ is preferably an aliphatic sulfonicacid anion substituted at α-position of sulfonic acid with a fluorineatom, an aromatic sulfonic acid anion substituted with a fluorine atomor a group having a fluorine atom, a bis(alkyl sulfonyl) imide anion inwhich the alkyl group is substituted with a fluorine atom, and atris(alkylsulfonyl)methide anion in which the alkyl group is substitutedwith a fluorine atom. The non-nucleophilic anion is, particularlypreferably, a perfluoro aliphatic sulfonic acid anion of 4 to 8 carbonatoms, and an aromatic sulfonic anion having a fluorine atom and, morepreferably, nonafluorobutane sulfonic acid anion, perfluorooctanesulfonic acid anion, pentafluorobenzene sulfonic acid anion, and3,5-bis(trifluoromethyl)benzene sulfonic acid anion.

Then, the compound (Z1-2) is to be described.

The compound (Z1-2) is a compound in a case where R₂₀₁ to R₂₀₃ in thegeneral formula (ZI) each independently represents an organic groupcontaining no aromatic ring. In this case, the aromatic ring alsoincludes aromatic rings containing hetero atoms.

The organic group containing no aromatic ring as R₂₀₁ to R₂₀₃ hasgenerally 1 to 30 carbon atoms, preferably, 1 to 20 carbon atoms.

R₂₀₁ to R₂₀₃ each independently represents, preferably, an alkyl group,cycloalkyl group, allyl group, or vinyl group, further preferably, alinear, branched, cyclic 2-oxoalkyl group, or alkoxycarbonyl methylgroup and, most preferably, the linear or branched 2-oxoalkyl group.

The alkyl group as R₂₀₁ to R₂₀₃ may be either linear or branched, andpreferably includes a branched alkyl group of 1 to 10 carbon atoms, forexample, a methyl group, ethyl group, propyl group, butyl group, orpentyl group. The alkyl group is, more preferably, a 2-linear orbranched oxoalkyl group, or alkoxycarbonyl methyl group.

The cycloalkyl group as R₂₀₁ to R₂₀₃ is preferably a cycloalkyl group of3 to 10 carbon atoms and includes, for example, a cyclopentyl group,cyclohexyl group, or norbornyl group. The cycloalkyl group is, morepreferably, 2-oxocycloalkyl group.

The 2-oxoalkyl group may be any of linear, branched and cyclic, andincludes preferably, a group having >C═O at the 2-position of the alkylgroup or cycloalkyl group.

The alkoxy group in the alkoxycarbonyl methyl group preferably includesalkyl groups of 1 to 5 carbon atoms (methyl group, ethyl group, propylgroup, butyl group, and pentyl group).

R₂₀₁ to R₂₀₃ may be substituted with a halogen atom, alkoxy group (forexample, of 1 to 5 carbon atoms), hydroxyl group, cyano group or nitrogroup).

Two of R₂₀₁ to R₂₀₃ may join to form a ring structure, and may have anoxygen atom, sulfur atom, ester bond, amide bond, or carbonyl group inthe ring. The group formed by joining two member of R₂₀₁ to R₂₀₃includes an alkylene group (for example, butylenes group and pentylenegroup).

The compound (Z1-3) is a compound represented by the following generalformula (Z1-3), which is a compound having a phenacyl sulfonium saltstructure.

R_(1c) to R_(5c) each independently represents a hydrogen atom, alkylgroup, cycloalkyl group, alkoxy group or halogen atom.

R_(6c) and R_(7c) each represents a hydrogen atom, alkyl group orcycloalkyl group.

R_(x) and R_(y) each independently represents an alkyl group, cycloalkylgroup, allyl group or vinyl group.

Any two or more of R_(1c) to R_(5c), and R_(x) and R_(y) may join toform a ring structure respectively, and the ring structure may have anoxygen atom, sulfur atom, ester bond, or amide bond.

Zc⁻ represents a non-nucleophilic anion, and includes those identicalwith the non-nucleophilic anion of X⁻ in the general formula (ZI).

The alkyl group as R_(1c) and R_(5c) is preferably a linear or branchedalkyl group of 1 to 20 carbon atoms, for example, a methyl group, ethylgroup, linear or branched propyl group, linear or branched butyl group,or linear or branched pentyl group.

The cycloalkyl group as R_(1c) and R_(7c) is preferably a cycloalkylgroup of 3 to 8 carbon atoms, for example, a cyclopentyl group, orcyclohexyl group.

The alkoxy group as R_(1c) and R_(7c) may be any of linear, branched orcyclic, and includes, for example, an alkoxy group of 1 to 10 carbonatoms, and preferably, a linear or branched alkoxy group of 1 to 5carbon atoms (for example, methoxy group, ethoxy group, linear orbranched propoxy group, linear or branched butoxy group, or linear orbranched pentoxy group), a cyclic alkoxy group of 3 to 8 carbon atoms(for example, cyclopentyloxy group, and cyclohexyloxy group).

Preferably, any one of R_(1c) and R_(5c) is linear or branched alkylgroup, cycloalkyl group or linear, branched or cyclic alkoxy group, andfurther preferably, the sum of the number of carbon atoms in R_(1c) toR_(5c) is 2 to 15. This can improve the solvent-solubility and suppressgeneration of particles during storage.

The alkyl group and cycloalkyl group as R_(x) and R_(y) are the same asthe alkyl group and cycloalkyl group for R_(1c) to R_(7c), and2-oxoalkyl group, 2-oxocycloalkyl group and alkoxycarbonyl methyl groupare more preferred.

The 2-oxoalkyl group and 2-oxocycloalkyl group include those having >C═Oat the 2-position of the alkyl group and cycloalkyl group as R_(1c) toR_(7c).

The alkoxy group in the alkoxycarbonyl methyl group includes thoseidentical with alkoxy groups as R_(1c) to R_(5c).

The group formed by joining R_(x) and R_(y) includes a butylenes group,pentylene group, etc.

R_(x) and R_(y) each represents, preferably, an alkyl group of 4 or morecarbon atoms, more preferably, an alkyl group of 6 or more carbon atoms,further preferably, an alkyl group of 8 or more carbon atoms.

In the general formulae (ZII) and (ZIII), R₂₀₄ to R₂₀₇ eachindependently represents an aryl group, alkyl group, or cycloalkylgroup.

The aryl group as R₂₀₄ to R₂₀₇ includes, preferably, a phenyl group andnaphthyl group, further preferably, a phenyl group.

The alkyl group as R₂₀₄ to R₂₀₇ includes, preferably, linear or branchedalkyl group of 1 to 10 carbon atoms, for example, a methyl group, ethylgroup, propyl group, butyl group, and pentyl group.

The cycloalkyl group as R₂₀₄ to R₂₀₇ includes cycloalkyl groups of 3 to10 carbon atoms, for example, cyclopentyl group, cyclohexyl group, andnorbornyl group.

The substituent which can be present in R₂₀₄ to R₂₀₇ includes, forexample, alkyl groups (of, for example, 1 to 15 carbon atoms),cycloalkyl groups (of, for example, 3 to 15 carbon atoms), aryl groups(of, for example, 6 to 15 carbon atoms), alkoxy groups (of, for example,1 to 15 carbon atoms), and halogen atom, hydroxyl group, and phenylthiogroup.

X⁻ represents a non-nucleophilic anion, and includes those identicalwith the non-nucleophilic anion as X⁻ in the general formula (ZI).

Preferred compound as the acid generator further includes compoundsrepresented by the following general formulae (ZIV), (ZV), and (ZVI).

In the general formula (ZIV), two Ar₃ each independently represents anaryl group.

R₂₀₈ in the general formulae (ZV) and (ZVI) each independentlyrepresents an alkyl group, cycloalkyl group or aryl group, in the samemanner as the alkyl group, cycloalkyl group, or aryl group as R₂₀₄ toR₂₀₇ in the general formulae (ZI) to (ZIII).

A represents an alkylene group, alkenylene group, or arylene group.

More preferred compounds among the acid generators include compoundsrepresented by the general formulae (ZI) to (ZIII).

Examples of the acid generators are described below, but the inventionis not limited thereto.

The acid generators can be used each alone or as a combination of two ormore of them.

The content of the acid generator in the positive type resistcomposition for liquid immersion exposure is preferably from 0.1 to 20mass %, more preferably, from 0.5 to 10 mass %, further preferably, from1 to 7 mass % based on the total solid content of the resistcomposition.

(C) Alkali Soluble Compound Having Alkyl Group of 5 or More CarbonAtoms.

The positive type resist composition for use in liquid immersionexposure according to the invention contains an alkali soluble compound(C) having an alkyl group of 5 or more carbon atoms.

Heretofore, when a resist with no problem in usual exposure is subjectedto liquid immersion exposure, development defects occurred frequently.However, since penetration of water during liquid immersion exposure canbe suppressed by the addition of the alkali soluble compound (C) havingan alkyl group of 5 or more carbon atoms, development defects and scumscan be decreased. Further, when the alkali soluble compound (C) is addedto a resist with large leaching amount to the liquid immersion solution,the effect of suppressing leaching can be obtained.

The alkali soluble compound (C) is a compound which is alkali-soluble,that is, a compound soluble to an alkali developer (ordinarily, anaqueous alkaline solution having a pH of from 10.0 to 15.0 at 23° C.).

Therefore, the alkali-soluble compound (C) has an alkali soluble groupand/or a group which is solubilized by hydrolyzation with an alkalideveloper.

The alkali soluble group includes, for example, a phenolic hydroxylgroup, carboxylic acid group, fluorinated alcohol group, sulfonic acidgroup, sulfone amide group, (sulfonyl) (carbonyl) methylene group andactive methylene group. Specific examples of the active methylene groupinclude —C(═O)—CH₂—C(═O)—, —C(═O)—CHR—C(═O)— (where R represents analkyl group), (—C(═O)—CH(C(═O))₂—, —SO₂—CH₂—C(═O)—), etc.

Preferred alkali-soluble group includes, for example, carboxylic acidgroup, fluorinated alcohol group (preferably, hexafluoroisopropanol),sulfonic acid group and sulfone amide group.

The group which is solubilized by hydrolyzation with an alkali developerincludes, for example, a lactone group, ester group, sulfoneamide group,and acid anhydride, the lactone group, sulfoneamide group, and acidanhydride being preferred.

The amount of the alkali soluble group (acid group) is, preferably, from2 to 10 mmeq/g and, more preferably, from 2 to 8 mmeq/g as an acid valueof the alkali soluble compound (C). The acid value is based on themeasurement of the amount of potassium hydroxide (mg) necessary forneutralizing the compound.

The alkali soluble compound (C) has an alkyl group of 5 or more carbonatoms.

The alkyl group of 5 or more carbon atoms is preferably linear orbranched, and has preferably 6 or more carbon atoms, more preferably, 8or more carbon atoms. The upper limit for the number of carbon atoms ispreferably 100 or less, further preferably, 50 or less.

The alkyl group of 5 or more carbon atoms is preferably afluorine-substituted alkyl group, particularly, a perfluoroalkyl group(for example, perfluorooctyl group or perfluorobutyl group).

The number of fluorine atoms present in the fluorine-substituted alkylgroup is preferably from 5 to 100, more preferably, from 9 to 50.

The alkali-soluble compound (C) has alkyl groups of 5 or more carbonatoms in an amount, preferably, from 5 to 95 mass %, more preferably,from 10 to 80 mass % based on the molecular weight of the alkali solublecompound (C).

The alkali soluble compound may be either a low molecular compound or ahigh molecular compound (for example, a resin). The molecular weight ispreferably, from 300 to 200,000, more preferably, from 500 to 200,000,further preferably, from 500 to 100,000.

In a case where the alkali soluble compound is a resin, those describedbelow are preferred.

(a) The amount of residual monomers is, preferably, 0 to 10 mass %,further preferably, 0 to 5 mass %.(b) The molecular weight distribution (Mw/Mn: also referred to as degreeof dispersion) is usually within a range from 1 to 5, and those ranging,preferably, from 1 to 4, and further preferably from 1 to 3 are used.From the view point of resolution, resist configuration, side walls ofresist patterns, and roughness, the molecular weight distribution ispreferably 5 or less.

The addition amount of the alkali soluble compound (C) in the positivetype resist composition for liquid immersion exposure is preferably from1 to 60 mass %, more preferably from 1 to 40 mass %, most preferablyfrom 1 to 10 mass % on the basis of the total solid content of theresist composition.

In a case where the positive type resist composition for liquidimmersion exposure is a resist composition for ArF exposure, it ispreferred that the alkali soluble compound contains no aromatic ring.

The alkali soluble compounds may be used each alone or a plurality ofthem may be mixed.

In a case where the alkali soluble compound is a resin, is can besynthesized by ordinary methods (for example, radical polymerization asin the synthesis of the acid decomposable resin (A) described above).

The alkali soluble compound (C) is preferably a resin comprising atleast one repeating unit represented by the following general formulae(Ca) to (Cf).

In the general formulae (Ca) to (Cf), Xc's each independently representsa hydrogen atom, a methyl group or an alkyl group having 5 or morecarbon atoms.

Rc₁'s each independently represents a hydrogen atom, or an alkyl grouphaving 5 or more carbon atoms.

Rc₂'s each independently represents an alkyl group having 5 or morecarbon atoms.

Rf₁ and Rf₂ each independently represents a hydrogen atom or an alkylgroup. At least one of Rf₁ and Rf₂ represents a fluorine-substitutedalkyl group.

Q represents a single bond or a divalent linking group.

Qc represents a single bond or a (nc+1)-valent linking group.

nc represents a positive integer, preferably represents a integer offrom 1 to 5, and more preferably represents a integer of 1 or 2.

The linking group preferably includes, although not particularlyrestricted, a single bond, alkylene group, cycroalkylene group, ethergroup, thioether group, carbonyl group, ester group, amide group,sulfoneamide group, urethane group and urea group, alone or incombination of two or more of them. Among them, alkylene group,cycroalkylene group and ester group alone or in combination of two ormore of them are specifically preferred.

Specific examples of the high molecular weight alkali soluble compound(resin) are described below, but they are not restricted to them.

A polymer containing a perfluoroalkyl group at the terminal end of thepolymer can be synthesized by using a chain transfer agent substitutedat the terminal end with the perfluoroalkyl group.

Examples of the low molecular weight alkali-soluble compound (C) aredescribed below, but they are not restricted to the examples.

(D) Organic Solvent

The positive type resist composition for liquid immersion exposureaccording to the invention is used while being dissolved in apredetermined organic solvent.

The organic solvent which can be used includes, for example, ethylenedichloride, cyclohexanone, cyclopentanone, 2-heptanone, γ-butyrolactone,methylethyl ketone, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl etheracetate, propylene glycol monomethyl ether, propylene glycol monomethylether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate,methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethylpyruvate, propyl pyruvate, N,N-dimethyl formamide, dimethyl sulfoxide,N-methyl pyrrolidone, methoxy butanol, and tetrahydrofuran.

In the invention, a mixed solvent prepared by mixing a solvent having ahydroxyl group and a solvent having no hydroxyl group in the structuremay be used as the organic solvent.

The solvent having a hydroxyl group includes, for example, ethyleneglycol, ethylene glycol monomethyl ether, ethylene glycol monoethylether, propylene glycol, propylene glycol monomethyl ether, propyleneglycol monoethyl ether and ethyl lactate. Among which propylene glycolmonomethyl ether and ethyl lactate are preferred.

The solvent having no hydroxyl group includes, for example, propyleneglycol monomethyl ether acetate, ethylethoxy propionate, 2-heptanone,γ-butyrolactone, cyclohexanone, butyl acetate, N-methyl pyrrolidone,N,N-dimethyl acetoamide and dimethyl sulfoxide, among which propyleneglycol monomethyl ether acetate, ethyl ethoxy propionate, 2-heptanone,γ-butyrolactone, cyclohexanone, and butyl acetate are preferred, andpropylene glycol monomethyl ether acetate, ethylethoxy propionate and2-heptanone are more preferred.

The mixing ratio (mass) of the solvent having a hydroxyl group and thesolvent having no hydroxyl group is preferably, from 1/99 to 99/1, morepreferably, from 10/90 to 90/10, further preferably, from 20/80 to60/40. A mixed solvent containing 50 mass % or more of the solventhaving no hydroxyl group is particularly preferred in view of theuniformity upon coating.

By using such a solvent, a resist composition at a solid concentrationusually from 3 to 25 mass %, preferably, from 5 to 22 mass %, morepreferably, from 7 to 20 mass %, further preferably, from 5 to 15 mass %is prepared.

(E) Organic Basic Compound

The composition of the invention, with an aim of preventing agingfluctuation of the performance after the irradiation of the actinic rayor the radiation to the heat treatment (T-tope shape formation of thepattern, sensitivity fluctuation, fluctuation of pattern line width,etc.), aging fluctuation of performance after coating and, further,excessive diffusion of acid (degradation of resolution) afterirradiation of the actinic ray or the radiation and during heattreatment, an organic basic compound can be used. The organic basiccompound is, for example, an organic basic compound containing a basicnitrogen, and those compounds with a pKa value of a conjugated acid of 4or more are used preferably.

Specifically, the following formulae (A) to (E) can be mentioned.

where R²⁵⁰, R²⁵¹ and R²⁵² may be identical with or different from eachother, and each represents an alkyl group of 1 to 20 carbon atoms,cycloalkyl group of 1 to 20 carbon atoms, or aryl group of from 6 to 20carbon atoms, in which R²⁵¹ and R²⁵² may join to each other to form aring. A substituent which may be present in each of the groups includesan amino group and hydroxyl group.

R²⁵³, R²⁵⁴, R²⁵⁵ and R²⁵⁶ may be identical with or different from eachother, and each represents an alkyl group of 1 to 6 carbon atoms.

Preferred examples include, for example, guanidine, aminopyridine,aminoalkylpyridine, aminopyrrolidine, indazole, imidazole, pyrazole,pyrazine, pyrimidine, purine, imidazoline, pyrazoline, piperazine,aminomorpholine, and aminoalkyl morpholine. Those compounds may have asubstituent, and preferred substituent includes, for example, an aminogroup, aminoalkyl group, alkylamino group, aminoaryl group, arylaminogroup, alkyl group, alkoxy group, acyl group, acyloxy group, aryl group,aryloxy group, nitro group, hydroxyl group, and cyano group.

Particularly preferred compounds include, for example, guanidine,1,1-dimethyl guanidine, 1,1,3,3-tetramethyl guanidine, imidazole,2-methylimidazole, 4-methyl imidazole, N-methyl imidazole,2-phenylimidazole, 4,5-diphenyl imidazole, 2,4,5-triphenyl imidazole,2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-dimemthylaminopyridine, 4-dimethylamino pyridine, 2-diethyl aminopyridine,2-(aminomethyl)pyridine, 2-amino-3-methyl pyridine, 2-amino-4-methylpyridine, 2-amino-5-methyl pyridine, 2-amino-6-methyl pyridine,3-aminoethyl pyridine, and 4-aminoethyl pyridine.

3-aminopyrolidine, piperazine, N-(2-aminoethyl) peperazine,N-(2-aminoethyl)pyperidine, 4-amino-2,2,6,6-tetramethyl piperidine,4-piperidino piperidine, 2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine,pyrazole, 3-amino-5-methyl pyrazole, 5-amino-3-methyl-1-p-tolylpyrazole,pyrazine, 2-(aminomethyl)-5-methyl pyrazine, pyrimidine,2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pirazoline,3-pirazoline, N-aminomorpholine, and N-(2-aminoethyl)morpholine, but,they are not restricted to them.

In addition, basic ammonium salts can be used. Specific examples of thebasic ammonium salts can include those compounds described below, butthey are not restricted to them.

Specifically, they include ammonium hydroxide, ammonium triflate,ammonium pentaflate, ammonium heptaflate, ammonium nonaflate, ammoniumundecaflate, ammonium tridecaflate, ammonium pentadecaflate, ammoniummethyl carboxylate, ammonium ethyl carboxylate, ammonium propylcarboxylate, ammonium butyl carboxylate, ammonium heptyl carboxylate,ammonium hexyl carboxylate, ammonium octyl carboxylate, ammonium nonylcarboxylate, ammonium decylcarboxylate, ammonium undecylcarboxylate,ammonium dodecadecyl carboxylate, ammonium tridecyl carboxylate,ammonium tetradecyl carboxylate, ammonium pentadecyl carboxylate,ammonium hexadecyl carboxylate, ammonium heptadecyl carboxylate, andammonium octadecyl carboxylate.

The ammonium hydroxide described above includes specifically,tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide,tetrapropyl ammonium hydroxide, tetrabutyl ammonium hydroxide,tetrapentyl ammonium hydroxide, tetrahexyl ammonium hydroxide,tetraheptyl ammonium hydroxide, methyl trioctyl ammonium hydroxide,tetraoctyl ammonium hydroxide, didecyldimethyl ammonium hydroxide,tetrakisdecyl ammonium hydroxide, dodecyl trimethyl ammonium hydroxide,dodecylethyl dimethyl ammonium hydroxide, didodecyl dimethyl ammoniumhydroxide, tridodecylmethyl ammonium hydroxide, myristylmethyl ammoniumhydroxide, dimethylditeradecyl ammonium hydroxide, hexadecyl trimethylammonium hydroxide, octadecyl trimethyl ammonium hydroxide, dimethyldioctadecyl ammonium hydroxide, tetraoctadecyl ammonium hydroxide,diallyldimethyl ammonium hydroxide, (2-chloroethyl)-trimethyl ammoniumhydroxide, (2-bromoethyl)trimethyl ammonium hydroxide,(3-bromopropyl)-trimethyl ammonium hydroxide, (3-bromopropyl)triethylammonium hydroxide, glycidyl trimethyl ammonium hydroxide, cholinehydroxide, (R)-(+)-(3-chloro-2-hydroxypropyl)trimethyl ammoniumhydroxide, (S)-(−)-(3-chloro-2-hydroxypropyl)-trimethyl ammoniumhydroxide, (3-chloro-2-hydroxypropy)-trimethyl ammonium hydroxide,(2-aminoethyl)-trimethyl ammonium hydroxide, hexamethonium hydroxide,decamethonium hydroxide, 1-azoniaproperane hydroxide, petroniumhydroxide, 2-chloro-1,3-dimethyl-2-imidazolinium hydroxide, and3-ethyl-2-methyl-2-thiazolinium hydroxide.

The organic basic compounds can be used by one or more and morepreferably, by two or more of them.

The amount of the organic basic compound to be used is usually, from0.001 to 10 mass %, preferably, from 0.01 to 5 mass % on the basis ofthe solid content of the positive type resist composition for liquidimmersion exposure.

The ratio between the acid generator and the organic basic compound tobe used in the composition, that is, acid generator/organic basiccompound (molar ratio) is, preferably, from 2.5 to 300. Namely, themolar ratio is preferably 2.5 or more in view of the sensitivity and theresolution, and is preferably 300 or less in view of suppression ofdegradation of the resolution due to the thickening with the of theresist pattern up to the heating treatment after exposure. The acidgenerator/organic basic compound (molar ratio) is, more preferably, from5.0 to 200, further preferably, from 7.0 to 150.

(F) A Dissolution Inhibitive Compound which is Decomposed Under theEffect of Acid and Increases the Solubility in an Alkali Developer

The positive type resist composition for use in liquid immersionexposure according to the invention can contain a solution inhibitivecompound that is decomposed under the effect of an acid and increasesthe solubility in the alkali developer (hereinafter also referred to asa “solution inhibitive compound”).

As the solution inhibitive compound, cycloaliphatic compounds oraliphatic compounds containing acid decomposable groups such as cholicacid derivatives containing acid decomposable groups as described in theproceeding of SPIE, 2724, 355 (1996) are preferred in order not to lowerthe transmittance at 220 nm or less. The acid decomposable group and thecycloaliphatic structure include those identical as described for theacid decomposable resin (A).

The molecular weight of the solution inhibitive compound is, preferably,3,000 or less, more preferably, from 300 to 3,000 and, furtherpreferably, from 500 to 2,500.

The addition amount of the dissolution inhibitive compound is,preferably, from 1 to 30 mass %, more preferably, from 2 to 20 mass %based on the entire solid content of the positive type resistcomposition for liquid immersion exposure.

Specific examples of the dissolution inhibitive compound is to bedescribed below, but it is not restricted to them.

(G) Surfactant

The positive type resist composition for liquid immersion exposureaccording to the invention can further contain a surfactant (G). Thesurfactant includes preferably, a fluorine-based and/or a silicon-basedsurfactant (a fluorine-based surfactant, a silicon-based surfactant, ora surfactant having both a fluorine atom and a silicon atom), or two ormore of them.

Since the resist composition for liquid immersion exposure according tothe invention contains the surfactant (G), it has enhancing effect onthe sensitivity, resolution, adhesiveness, suppression of developmentfailure, etc. upon use of exposure light source at 250 nm or less,particularly, 220 nm or less.

The fluorine-based and/or silicon-based surfactants, can includesurfactants disclosed in, for example, JP-A Nos. 62-36663, 61-226746,61-226745, 62-170950, 63-34540, 7-230165, 8-62834, 9-54432, 9-5988,Japanese Patent Application No. 2002-277862, U.S. Pat. Nos. 5,405,720,5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511, and5,824,451, and commercially available surfactants described below canalso be used as they are.

Commercially available surfactants include, for example, fluorine-basedor silicone-based surfactants such as F-top EF301, and EF303(manufactured by Shin-Akita Kasei K.K.), Florad FC430, 431 and 4430(manufactured by Sumitomo 3M, Inc.), Megafac F171, F173, F176, F189,F113, F110, F117, F120 and R08 (manufactured by Dainippon Ink andChemicals, Inc.), Surflon S-382, SC101, 102, 103, 104, 105, and 106,(manufactured by Asahi Glass Co., Ltd.), Troysol S-366 (manufactured byTroy Chemical Industries, Inc.), F-top EF121, EF122A, EF122B, RF122C,EF125M, EF135M, EF351, 352, EF801, EF802, EF 601 (manufactured by JEMCOInc.), PF636, PF656, PF6320, PF6520 (manufactured by OMNOVA SOLUTIONS,INC.), FTX-204D, 2080, 2180, 230G, 204D, 208D, 212D, 218, 222D(manufactured by NEOS) etc. Further, a polysiloxane polymer KP-341(manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used as thesilicon-based surfactant.

In addition to the known surfactants described above, surfactants usingpolymers having a fluoro aliphatic group derived from a fluoro aliphaticcompound produced by a telomerization method (also referred to as atelomer method) or an oligomerization method (also referred to asoligomer method) can also be used. The fluoro aliphatic compound can besynthesized by a method described in JP-A No. 2002-90991.

As the polymer having a fluoro aliphatic group, copolymers of monomershaving a fluoro aliphatic group and a (poly(oxyalkylene))acrylate and/or(poly(oxyalkylene)) methacrylate are preferred, and they may bedistributed at random or block-copolymerized. The poly(oxyalkylene)group includes poly(oxyethylene) group, poly(oxypropylene) group,poly(oxybutylene) group, etc, and, in addition, may be a unit havingalkylenes of different chain length in the same chain, for example,poly(block-connected form of oxyethylene and oxypropylene andoxyethylene) and poly(block connection form of oxyethylene andoxypropylene), etc. Further, the copolymer of the monomers having afluoro aliphatic group and (poly(oxyalkylene))acrylate(or methacrylate)includes not only binary copolymers but also ternary or highercopolymers formed by simultaneously copolymerizing monomers having twoor more different fluoro aliphatic groups and two or more different(poly(oxyalkylene))acrylates (or methacrylates).

For example, the commercially available surfactants include MegafacF178, F-470, F-473, F-475, F-476, and F-472 (manufactured by DainipponInk and Chemicals, Inc.). In addition, they include copolymers ofacrylate (or methacrylate) having a C₆F₁₃ group and (poly(oxyalkylene))acrylate (or methacrylate), and copolymers of acrylate (or methacrylate)having a C₃F₇ group, (poly(oxyethylene)) acrylate (or methacrylate) and(poly(oxypropylene)) acrylate (or methacrylate), etc.

In the invention, surfactants other than the fluorine-based and/orsilicon-based surfactants can also be used. Specifically, they includenonionic surfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkyl allyl ethers such as polyoxyethylene octyl phenolether and polyoxyethylene nonyl phenol ethers, sorbitan fatty acidesters such as polyoxyethylene.polyoxypropylene block copolymers,sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,sorbitan monooleate, sorbitan trioleate, and sorbitan tristearate, andpolyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate.

In the invention, surfactants represented by the following generalformula (W) may also be used.

In the general formula (W),

R_(w) represents a hydrogen atom or an alkyl group,

m represents an integer of 1 to 30,

n represents 0 or an integer of 1 to 3, and

p represents 0 or an integer of 1 to 5.

The alkyl group in R_(w) is preferably a linear or branched alkyl groupof 1 to 5 carbon atoms and includes, for example, a methyl group, ethylgroup, propyl group, n-butyl group, sec-butyl group, and t-butyl group.Among them, methyl group, ethyl group and propyl group are preferred.

In the general formula (W), it is preferred that m represents an integerof 1 to 25, n is an integer of 0 to 2, and p is an integer of 0 to 3.

Preferred examples of the surfactant represented by the general formula(W) include, for example, commercially available PF 636 (n=0, m=6, p=1,and R₁=methyl group in the general formula (W)), PF 6320 (n=0, m=20,p=1, and R₁=methyl group), PF656 (n=1, m=6, p=1, and R₁=methyl group inthe general formula (W), and PF 6520 (n=1, m=20, p=1, and R₁=methylgroup in the general formula (W)), (all manufactured by OMNOVASOLUTIONS, INC.).

The surfactants may be used each alone, or may be used as a combinationof several of them.

The amount of surfactant (G) to be used is preferably, from 0.01 to 5mass %, more preferably, from 0.1 to 3 mass % based on the entire amountof the resist composition for liquid immersion exposure (except forsolvent).

(H) Alkali Soluble Resin

The positive type resist composition for liquid immersion exposureaccording to the invention can further be incorporated with a resinwhich is soluble to an alkali developer, whereby the sensitivity isimproved.

In the invention, novolac resins having a molecular weight of 1,000 to20,000 or polyhydroxystyrene derivatives having a molecular weight ofabout from 3,000 to 50,000 can be used as such a resin. However, sincethey have large absorption relative to the light of 250 nm or less, itis preferred that they are used while being partially hydrogenated, orused in an amount of 30 mass % or less based on the entire amount of theresin.

In addition, resins having a carboxyl group as an alkali soluble groupmay also be used. The resin having the carboxyl group preferably has amono-nuclear or poly-nuclear cycloaliphatic hydrocarbon group forimproving the dry etching resistance. Specifically, they include acopolymer of a methacrylic acid ester having a cycloaliphatichydrocarbon structure showing no acid decomposability and a(meth)acrylic acid or a resin of (meth)acrylic acid ester of acycloaliphatic hydrocarbon group having a carboxyl group at theterminal.

The addition amount of such alkali soluble resin is usually 30 mass % orless based on the total amount of the resin including the aciddecomposable resin (A).

(I) Carboxylic Acid Onium Salt

The positive type resist composition for liquid immersion exposureaccording to the invention may be incorporated with a carboxylic acidonium salt.

The carboxylic acid onium salts in the invention includes carboxylicacid sulfonium salt, carboxylic acid iodonium salts, carboxylic acidammonium salts, etc. Particularly, as the carboxylic acid onium salts,iodonium salts and sulfonium salts are preferred. Further, it ispreferred that the carboxylate residue in the carboxylic acid onium saltcontains no aromatic group or carbon-carbon double bond. Especiallypreferred anion moiety includes linear, branched, mononuclear orpolynuclear alkyl carboxylic acid anions having 1 to 30 carbon atoms.Further anions of carboxylic acid in which the alkyl groups arepartially or entirely substituted with fluorine are more preferred. Thealkyl chain may be incorporated with oxygen atoms. This can ensure thetransparency relative to the light of 220 nm or less, improve thesensitivity and resolution, and improve the density dependence andexposure margin.

The anions of fluoro-substituted carboxylic acid include anions offluoroacetic acid, nonafluoropentanoic acid, perfluorododecanoic acid,perfluorotridecanoic acid, difluoroacetic acid, trifluoroacetic acid,pentafluoropropionic acid, heptafluorobutyric acid, perfluorocyclohexanecarboxylic acid, 2,2-bistrifluoromethyl propionic acid, etc.

Those carboxylic acid onium salts can be synthesized by reactingsulfonium hydroxide, iodonium hydroxide, ammonium hydroxide, oncarboxylic acid with a silver oxide in an appropriate solvent.

The content of the carboxylic acid onium salt in the composition isappropriately from 0.1 to 20 mass %, preferably, from 0.5 to 10 mass %,further preferably, from 1 to 7 mass % based on the total solid contentof the positive type resist composition for liquid immersion exposure.

(J) Other Additives

The positive resist composition for liquid immersion exposure canfurther be incorporated optionally with dyes, plasticizers,photosensitizers and compounds for accelerating the solubility to liquiddeveloper (for examples, phenol compounds having a molecular weight of1,000 or less, cycloaliphatic or aliphatic compounds having a carboxylicgroup), etc.

Such phenol compounds having a molecular weight of 1,000 or less caneasily be synthesized by those skilled in the art with reference to themethod described in JP-A Nos. 4-122938, and 2-28531, and U.S. Pat. No.4,916,210, and EP No. 219,294.

Specific examples of the cycloaliphatic or aliphatic compounds having acarboxylic group include carboxylic acid derivatives having a steroidstructure such as cholic acid, deoxycholic acid, and lithocholic acid,adamantane carboxylic acid derivatives, adamantane dicarboxylic acid,cyclohexane carboxylic acid and cyclohexane dicarboxylic acid, but theyare not restricted to them.

The metal content in the positive type resist composition for liquidimmersion exposure of the invention is preferably 100 ppb or less.

(K) Pattern Forming Method

The positive type resist composition for liquid immersion exposureaccording to the invention is used by dissolving the ingredientsdescribed above in a predetermined organic solvent, preferably, themixed solvent described above, and then coating it on a predeterminedsupport as described below.

Namely, the positive type resist composition for liquid immersionexposure is coated at a predetermined thickness (usually, from 50 to 500nm) on a substrate (for example, silicone/silicon dioxide coating) whichis used for the manufacture of precise integrated circuit elements by anappropriate coating method such as by a spinner or a coater.

After coating, the resist is dried by spinning or baking to form aresist film, then subjected to exposure by way of a liquid immersionsolution (liquid immersion exposure) through a mask, etc. for forming apattern. The exposure amount can be appropriately determined and it isusually from 1 to 100 mJ/cm². After the exposure, spinning and/or bakingis preferably conducted, development and rinsing are carried out toobtain a pattern. Preferably, baking is conducted after the exposure,and the temperature for the baking is usually from 30 to 300° C. With aview point of PED described above, it is preferred that the period oftime from the exposure to the baking step is shorter.

The light for the exposure is far ultraviolet rays at a wavelengthpreferably of 250 nm or less, more preferably, 220 nm or less.Specifically, they include KrF excimer laser (248 nm), ArF excimer laser(193 nm) F₂ excimer laser (157 nm) and X rays, etc.

Incidentally, the change in performance of the resist when beingsubjected to the liquid immersion exposure is thought to be due to thecontact between the surface of the resist and the liquid immersionsolution.

The liquid immersion solution used upon liquid immersion exposure is tobe described below.

The liquid immersion solution is preferably a liquid which istransparent to the exposure wavelength and having a temperaturecoefficient of the refractive index as small as possible such that thestrength of the optical images projected on the resist is minimized.Particularly, in a case where the exposure light source is an ArFexcimer laser (wavelength: 193 nm), use of water is preferred in view ofeasy availability and easy handling in addition to the view pointsdescribed above.

For the purpose of further improvement of refraction index, mediumhaving refraction index of 1.5 or more may be used.

In a case of using water as the liquid immersion solution, an additive(liquid) that does not dissolve the resist layer on the wafer and theeffect of which to the optical coating at the lower surface of the lensdevice is negligible may be added at a slight ratio in order to decreasethe surface tension of water and increase the surface activity. Theadditive is preferably an aliphatic alcohol having the refractive indexsubstantially equal with that of water and, specifically, it includes,for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, etc. Theaddition of the alcohol of the refractive index substantially equal withthat of water can provide a merit capable of decreasing the change ofthe refractive index as less as possible as the entire liquid even whenthe alcohol ingredient in water is evaporated to change theconcentration of the content. On the other hand, in a case where asubstance not transparent to a light at 193 nm or impurities having arefractive index greatly different from that of water should be mixed,since this causes distortion in the optical images projected over theresist, distilled water is preferred as water to be used. Further,purified water filtered by passing through an ion exchange filter or thelike may also be used.

The electric resistance of water is preferably 18.3 MΩ·cm or more andthe TOC (organic material concentration) is preferably 20 ppb or less.Further, deaeration is applied preferably.

The lithography performance can be improved by elevating the refractionindex of the liquid immersion solution. In view of this, additive forelevating the refraction index can be added in water, or heavy water(D₂O) may be used instead of water.

A film less soluble to the liquid immersion solution may also bedisposed between the resist film formed of the positive type resist foruse in the liquid immersion exposure and the liquid immersion solutionof the invention (hereinafter referred to as “top coat”), in order toavoid direct contact of the resist film with the liquid immersionsolution. The function necessary for the top coating is the coatingadaptability to the portion to the upper layer portion of the resist,transparency to radioactive rays, particularly, at 193 nm, and lesssolubility to the liquid immersion solution. It is preferred the topcoat is immiscible with the resist and, further, can be coated uniformlyto the upper layer of the resist.

A polymer not containing the aromatic ingredient is preferred for thetop coat in view of the transparency at 193 nm and includes, forexample, a hydrocarbon polymer acrylate ester polymer, polymethacrylicacid, polyacrylic acid, polyvinyl ether, silicon-containing polymer, andfluorine-containing polymer.

When the top coat is peeled, a liquid developer may be used or a peelingagent may be used separately. As the peeling agent, a solvent with lesspenetration to the resist is preferred. It is preferred that the resistcan be peeled by the alkali developer in that the peeling step can beapplied simultaneously with the developing step for the resist. With aview point of peeling by the alkali developer, the top coat ispreferably acidic and with a view point of non-intermixing property withthe resist, it may be either neutral or alkaline.

The resolution is improved in a case where there is no difference of therefractive index between the top coating and the liquid immersionsolution. In a case of using an ArF excimer layer (wavelength: 193 nm)as the exposure light source, since the use of water as the liquidimmersion solution is preferred, it is preferred that the refractiveindex of the top coating for use in ArF liquid immersion exposure issimilar with that of water (1.44). Further, with a view point oftransparency and refractive index, a thin film is more preferred.

In the case of using organic solvent as the liquid immersion solution,the top coating is preferably water-soluble.

As the alkali developer to be used in the developing step, there can beused, for example, inorganic alkalis such as sodium hydroxide, potassiumhydroxide, sodium carbonate, sodium silicate, sodium metasilicate, andaqueous ammonia, primary amines such as ethylamine and n-propylamine,secondary amines such as diethylamine and di-n-butyl amine, tertiaryamines such as triethylamine and methyldiethyl amine, alcohol aminessuch as dimethyl ethanolamine and triethanolamine, quaternary ammoniumsalts such as tetramethyl ammonium hydroxide and tetraethyl ammoniumhydroxide, and aqueous alkaline solution such as pyrrol and piperidine.

Further, the aqueous alkaline solutions may also be used with additionof an appropriate amount of alcohol or surfactant.

As a rinsing solution, purified water is used and it may also be usedwith addition of an appropriate amount of surfactant.

The alkali concentration of the alkali developer is usually from 0.1 to20 mass %.

The pH of the alkali developer is usually from 10.0 to 15.0.

After the developing treatment or the rinsing treatment, a treatment ofremoving the developer or the rinsing solution deposited on the patterncan be conducted with a supercritical fluid.

Example

The invention is to be described more specifically by way of examples,but the content of the invention is not restricted to them.

Synthesis of Resin (1)

2-adamantyl-2-propylmethacrylate, 3,5-dihydroxy-1-adamantyl methacrylateand norbornane lactone acrylate at a molar ratio of 40/20/40 (molarratio) and dissolved in propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether=40/40 (mass ratio) to prepare450 g of a solution with 22% solid concentration. To the solution, 1 mol% of a polymerization initiator, V-601 (dimethyl2,2′-azobis(2-methylpropionate) available from WAKO JUNYAKU KOGYO CO.was added, which was added dropwise under a nitrogen atmosphere to 50 gof a mixed solution of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether=60/40 (mass ratio) heated to100° C. over 6 hours. After the completion of addition, the reactionsolution was stirred for 2 hours. After the completion of the reaction,the reaction solution was cooled to a room temperature, a white powdercrystallized and deposited on 5 L of a mixed medium of hexane/ethylacetate=9/1 (mass ratio) was obtained through filtration to recover theaimed resin (1). By ¹³CNMR and polymer acid value measurement, thepolymer compositional ratio(2-adamantyl-2-propylmethacrylate/3,5-dihydroxy-1-adamantylmethacrylate/norbornane lactone acrylate (a/b/c) was determined as39/21/40 (molar ratio). As a result of GPC measurement, the weightaverage molecular weight (Mw) on the basis of standard polystyrene was9700, and the degree of dispersion (Mw/Mn) was 2.01.

The resins (2) to (20) which were used in the invention were synthesizedin the same manner as the method for the resin (1).

The structures of the resins (1) to (20) are described below.

Examples 1 to 27 and Comparative Examples 1 to 4 Preparation of Resist

Ingredients shown in the Table 1 were dissolved each in solvent toprepare solutions at 10 mass % concentration for solid content, andfiltered through a 0.1 μm polyethylene filter to prepare positive typeresist compositions for use in liquid immersion exposure. Each of thepositive type resist compositions for use in the liquid immersionexposure thus prepared was evaluated by the following method and theresults are shown in Table 1. When the ingredients are used inplurality, the ratio between them is expressed by mass ratio.

An organic antireflection film ARC 29A (manufactured by Nissan ChemicalCo.) was coated over a silicon wafer, and baked at 205° C. for 60 sec toform an anti-reflection film at 78 nm. A positive type resistcomposition for use in liquid immersion exposure thus prepared wascoated, and baked at 120° C. for 60 sec to form a resist film of 150 nm.The thus obtained wafer was put to 2-beam interference exposure by adevice shown in FIG. 1 using pure water as the liquid immersion solution(wet exposure). The wavelength of the laser used was 193 nm, and a prismforming a 90 nm line & space pattern was used. Just after exposure, itwas heated at 125° C. for 90 sec and then developed with an aqueoussolution of tetramethyl ammonium hydroxide (2.38 mass %) for 60 sec,rinsed with pure water and then spin-dried to obtain a resist pattern.

In the apparatus shown in FIG. 1, are shown a laser 1, a diaphragm 2, ashutter 3, reflection mirrors 4, 5, and 6, a condensing lens 7, a prism8, a liquid immersion solution 9, a wafer 10 provided with ananti-reflection film and a resist film, and a water stage 11.

<Evaluation Method> [Development Defect]

Number of development defects was measured for the resist patternobtained as described above by using KLA-2360 apparatus manufactured byKLA Tencor Japan and the obtained primary data values were used as theresult of measurement.

[Scum]

The remaining state of development residues in a resist pattern of 90 mmline width obtained as described above (scums) was observed by ascanning type electron microscope (S-9260, manufactured by Hitachi) andevaluated as A for those not observed with residues, as C for thoseobserved with considerable residues and as B for those therebetween.

[Leaching Amount of Generated Acid]

The prepared resist composition was coated on a 8 inch silicon wafer,and baked at 115° C. for 60 sec to form a resist film of 150 nm. Afterexposing the resist film by an exposure apparatus at a wavelength of 193nm for the entire surface at 50 mJ/cm² and then 5 ml of pure waterdeionized by using a super pure water manufacturing apparatus(Milli-QJr, manufactured by NIPPON MILLIPORE) was dropped on the resistfilm. After placing water, on the resist film for 50 sec, the water wassampled, and the concentration of the acid leached therein wasdetermined by LC-MS.

-   -   LC apparatus: 2695, manufactured by Water Co.    -   MS apparatus: Esquire 3000 plus manufactured by Bruke Kaltonics.        Co.

The concentration of the leached anion species of the photoacidgenerator (PAG) was measured by the LC-MS apparatus.

TABLE 1 Composition Evaluation Resin Photo acid Solvent SurfactantDissolution inhib- Alkali soluble Number of Leaching (2 g) generator(mg) (mass ratio) (5 mg) itive compound (g) compound (C) defects Scumdegree (%) Example 1 1 z2(20) SL-4/SL-6 W-1 —  (E-1) 300 A 5 (60/40) 2 2z2(24) SL-2/SL-4 W-2 — (D-1) 310 A 6 (50/50) 3 3 z6(28) SL-1/SL-4/SL-8W-3 —  (E-4) 320 A 7 (40/58/2) 4 4 z1(20) SL-2/SL-4 W-4 —  (E-2) 310 A 6(40/60) 5 5 z2(20) SL-2/SL-4 — — (D-2) 300 A 5 (40/60) 6 6 z6(20)SL-2/SL-4/SL-9 W-4 — (E-1)/(D-2) 330 A 7 (40/59/1) (10/90) 7 7 z6(20)SL-2/SL-4 W-1 — (D-1)/(E-7) 310 A 8 z9(15) (50/50) (50/50) 8 8 z38(20) SL-2/SL-6 W-1 — (D-4) 360 B 12 (70/30) 9 9 z2(30) SL-2/SL-4/SL-9 W-1 — (E-1) 310 A 6 (40/59/1) 10 10 z2(25) SL-2/SL-4 W-2 — (D-1)/(D-5) 300 B8 (40/60) (70/30) 11 11 z38(12)  SL-2/SL-4 W-3 — (E-1)/(E-7) 330 A 7z2(25) (40/60) (90/10) 12 12 z6(12) SL-2/SL-4 W-4 — (D-1)/(D-3) 270 A 2z31(10)  (40/60) (70/30) 13 13 z6(22) SL-1/SL-7 W-4 I-1 (D-3) 280 A 3z25(10)  (40/60) (0.1) 14 14 z2(32) SL-4/SL-6 W-1 —   (E-22) 320 A 7(60/40) 15 15 x38(40)  SL-3/SL-7 W-3 — (D-1)/(D-2) 310 A 8 (60/40)(70/30) 16 16 z3(33) SL-2/SL-5 W-2 — (D-1)/(E-7) 310 A 6 (60/40) (20/80)17 17 z2(50) SL-2/SL-7 W-2 I-2 (D-4) 350 B 13 (60/40) (0.1) 18 18z38(27)  SL-2/SL-7 W-1 — (D-3) 280 A 2 (60/40) 19 19 z6(29) SL-2/SL-7W-1 — (D-1)/(D-2) 310 A 6 (60/40) (80/20) 20 20 z3(25) SL-2/SL-4 W-4 —(D-3) 300 A 5 (40/60) 21 1 z55(100) SL-2/SL-4 W-1 — (D-6) 270 A 8(40/60) 22 2 z55(80)  SL-2/SL-4 W-1 — (D-7) 310 A 5 (30/70) 23 1z56(20)  SL-4/SL-6 W-2 — (D-8) 300 A 8 z14(10)  (60/40) 24 1 z34(120)SL-2/SL-4 W-2 — (D-9) 280 A 6 (30/70) 25 2 z60(5)  SL-2/SL-4 W-1 — (D-9)280 A 6 z67(40)  (40/60) 26 2 z67(40)  SL-2/SL-4 W-1 — (D-9) 280 A 8(40/60) 27 1 z55(30)  SL-4/SL-6 W-4 —  (D-10) 300 A 8 z60(10)  (60/40)Comparative 1 1 z2(24) SL-4/SL-6 W-1 — — 650 C 30 Example (60/40) 2 2z2(24) SL-2/SL-4 W-1 — — 670 C 32 (60/40) 3 3 z2(24) SL-4/SL-6 W-1 — —620 C 35 (60/40) 4 4 z2(24) SL-4/SL-6 W-l — — 650 C 33 (60/40)

The symbols in Table 1 are as follows.

Acid generators correspond to those exemplified above.

-   SL-1: cyclopentanone-   SL-2: cyclohexanone-   SL-3: 2-methylcyclohexanone-   SL-4: propylene glycol monomethyl ether acetate-   SL-5: ethyl lactate-   SL-6: propylene glycol monomethyl ether-   SL-7: 2-heptanone-   SL-8: γ-butyrolactone-   SL-9: propylene carbonate-   W-1: Megafac F176, (manufactured by Dainippon Ink and Chemicals,    Inc.) (Fluoro type)-   W-2: Megafac R08, (manufactured by Dainippon Ink and Chemicals,    Inc.) (Fluoro and silicon type)-   W-3: Polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical    Co., Ltd.) (Silicon type)-   W-4: Troysol S-366 (manufactured by Troy Chemical Industries, Inc.).-   I-1: t-butyl lithocholate-   I-2: t-butyl adamantane carboxylate

[Low Molecular Alkali Soluble Compound]

-   E-1: A compound having an alkali soluble group exemplified above,    with an acid value of 2.6 mm equivalent/g.-   E-2: A compound having an alkali soluble group exemplified above,    with an acid value of 2.4 mm equivalent/g.-   E-4: A compound having an alkali soluble group exemplified above,    with an acid value of 5.0 mm equivalent/g.-   E-7: A compound having an alkali soluble group exemplified above,    with an acid value of 3.6 mm equivalent/g.-   E-22: A compound having an alkali soluble group exemplified above    formed by hydrolysis by the alkali developer exemplified above, with    an acid value of 0.0 mm equivalent/g.

[High Molecular Alkali Soluble Compound]

-   (D-1) to (D-10): High molecular alkali soluble compounds shown in    Table 2 (resins).

The repetitive unit constitutions (C-1), (C-7), (C-19), (C-23) and(C-31) to (C-33) in Table 2 mean repetitive unit constitutions of thealkali soluble compounds exemplified above (resins). The compositionalratios are molar ratios of the repetitive units. The unit of the acidvalue is mm equivalent/g.

Alkali soluble Constitution of Compositional Molecular Dispersion Acidcompound repetitive units ratio weight degree value (D-1) (C-1) 50/5010000 1.4 3.9 (D-2) (C-1) 70/30 15000 1.4 6.3 (D-3) (C-7) 50/50 8000 1.31.6 (D-4) (C-19) 50/50 8000 1.4 2.4 (D-5) (C-23) 50/50 8000 1.3 2.8(D-6) (C-31) 80/20 12000 2.1 4.4 (D-7) (C-31) 60/40 5000 1.8 3.1 (D-8)(C-32) 70/30 12000 1.5 2.0 (D-9) (C-33) 80/20 7000 1.7 2.0 (D-10) (C-33)60/40 7000 1.8 1.6

The results of Table 1 show that, upon liquid immersion exposure, thepositive type resist composition for liquid immersion exposure accordingto the invention has small number of development defects and scum, andthat the leaching thereof to the liquid immersion solution issuppressed.

The present invention can provide a positive type resist compositionsuitable to liquid immersion exposure suppressing development defects,scums and leaching of the resist ingredient to the liquid immersionsolution during liquid immersion exposure, as well as a method offorming a pattern using the same.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

What is claimed is:
 1. A resist composition for ArF exposure,comprising; (A) a resin having a monocyclic or polycyclic cycloaliphatichydrocarbon structure, the resin increasing its solubility in an alkalideveloper by an action of acid; (B) a compound generating acid uponirradiation with one of an actinic ray and a radiation; (C) a resincontaining an alkyl group having 2 or more carbon atoms; and (D) asolvent; and wherein the structure of resin (A) and the structure ofresin (C) are not in the same compound.
 2. The resist composition forArF exposure according to claim 1, wherein a content of the resin (C) is1 to 10 mass % on the basis of the total solid content of the resistcomposition.
 3. The resist composition for ArF exposure according toclaim 2, wherein the resin (C) contains an unsubstituted alkyl grouphaving 2 to 20 carbon atoms.
 4. The resist composition for ArF exposureaccording to claim 3, wherein the resin (C) contains a repeating unitderived from a (meth)acrylic acid derivative having an unsubstitutedalkyl group having 2 to 20 carbon atoms.
 5. The resist composition forArF exposure according to claim 4, wherein the resin (A) contains alactone group.
 6. The resist composition for ArF exposure according toclaim 5, wherein the resin (A) contains no aromatic group.
 7. The resistcomposition for ArF exposure according to claim 1, wherein the resin (C)contains an alkyl group having 5 or more carbon atoms.
 8. The resistcomposition for ArF exposure according to claim 7, wherein the resin (C)contains a fluorinated alkyl group having 5 or more carbon atoms.
 9. Theresist composition for ArF exposure according to claim 7, wherein theresin (C) contains an alkali soluble group.
 10. The resist compositionfor ArF exposure according to claim 9, wherein the resin (C) contains acarboxyl group as the alkali soluble group.
 11. The resist compositionfor ArF exposure according to claim 9, wherein the resin (C) contains afluorinated alcohol as the alkali soluble group.
 12. The resistcomposition for ArF exposure according to claim 7, wherein the resin (C)contains a group which is solubilized by hydrolyzation with an alkalideveloper.
 13. The resist composition for ArF exposure according toclaim 12, wherein the resin (C) contains a lactone group as the groupwhich is solubilized by hydrolyzation with an alkali developer.
 14. Theresist composition for ArF exposure according to claim 12, wherein theresin (C) contains an ester group as the group which is solubilized byhydrolyzation with an alkali developer.
 15. The resist composition forArF exposure according to claim 12, wherein the resin (C) contains asulfone amide group as the group which is solubilized by hydrolyzationwith an alkali developer.
 16. A resist film formed by using the resistcomposition for ArF exposure according to claim
 1. 17. A pattern formingmethod, comprising exposing the resist film according to claim 16 withan ArF excimer laser.
 18. The pattern forming method according to claim17, wherein the exposing is an immersion exposure.